COMPUTER TECHNOLOGY IN 2020

NANO TECHNOLOGY

Here's a date for your diary November 1st, 2011. According to a group of

researchers calling themselves the Nanocomputer Dream Team, that's the day

they'll unveil a revolutionary kind of computer, the most powerful ever seen.

Their nanocomputer will be made out of atoms.

First suggested by Richard Feynman in 1959, the idea of nanotechnology,

constructing at the atomic level, is now a major research topic worldwide.

Theoreticians have already come up with designs for simple mechanical

structures like bearings, hinges, gears and pumps, each made from a few

collections of atoms. These currently exist only as computer simulations, and

the race is on to fabricate the designs and prove that they can work.

Moving individual atoms around at will sounds like fantasy, but it's already

been demonstrated in the lab. In 1989, scientists at IBM used an electron

microscope to shuffle 35 xenon atoms into the shape of their company's logo.

Since then a team at IBM's Zurich labs has achieved the incredible feat of

creating a working abacus on the atomic scale.

Each bead is a single molecule of buckminsterfullerene (a buckyball),

comprising 60 atoms of carbon linked into a football shape. The beads slide up

and down a copper plate, nudged by the tip of an electron microscope.

The Nanocomputer Dream Team wants to use these techniques to build an

atomic computer. Such a computer, they say can then be used to control

simple molecular construction machines, which can then build more complex

molecular devices, ultimately giving complete control of the molecular world.

The driving force behind the Dream Team is Bill Spence, publisher of

Nanotechnology magazine. Spence is convinced that the technology can be

made to work, and has enlisted the help of over 300 enthusiasts with diverse

backgrounds - engineers, physicists, chemists, programmers and artificial

intelligence researchers. The whole team has never met, and probably never

will. They communicate by email and pool their ideas on the Web. There's only

one problem. Nobody is quite sure how to build a digital nanocomputer.

The most promising idea is rod logic, invented by nanotechnology pioneer

Eric Drexler, now chairman of the leading nano think tank The Foresight

Institute. Rod logic uses stiff rods made from short chains of carbon atoms.

Around each rod sits a knob made of a ring of atoms. The rods are fitted into

an interlocking lattice, where each rod can slide between two positions, and be

reset by a spring made of another few atoms. Drexler has shown how to use

such an arrangement to achieve the effect of a conventional electronic

transistor, where the flow of current in one wire is switched on and off by

current in a different wire. Once you have transistors, you can build a NAND

gate. From NAND gates you can construct every other logic element a

computer needs.

Apart from the immensely difficult problem of physically piecing together

these molecular structures, massive calculations are required to determine if

particular molecular configurations are even possible. The Dream Team will

perform these molecular simulation calculations using metacomputing where

each person's PC performs a tiny part of the overall calculation, and the

results are collated on the Web. There are already prototype tools for

experimenting with molecular configurations, such as NanoCAD, a freeware

nano design system including Java source code.

This may all sound like pie in the sky, but there's serious research and

development money being spent on nanotechnology. A recent survey counted

over 200 companies and university research groups working in the field. And

April 1997 saw the foundation of Zyvex, the world's first nanotechnology

manufacturing company. Zyvex's goal is to build an assembler, the basic

element required for nanotechnology. The assembler will itself be a machine

made from molecules, fitted with atom sized tools for manipulating other

molecules to build other machines. It will also be capable of replicating itself

from the materials around it.

While they may lack any actual working prototypes of their technology,

nanotechnologists are certainly not short of ideas. Once you have the ability to

make molecular machines, the possibilities are amazing and often bizarre. One

idea is utility fog, where billions of submicroscopic molecular robots each

containing a nanocomputer are linked together to form a solid mass.

Controlled by a master nanocomputer, the robots could alter their

configurations to create any object you like.

Nanotechnology does come with one tiny drawback, however. What happens if

a molecular machine goes haywire, and instead of building, starts demolishing

the molecules around it? The world would quite literally fall apart.

OPTICAL COMPUTER

In most modern computers, electrons travel between transistor switches on

metal wires or traces to gather, process and store information. The optical

computers of the future will instead use photons traveling on optical fibers or

thin films to perform these functions. But entirely optical computer systems

are still far into the future. Right now scientists are focusing on developing

hybrids by combining electronics with photonics. Electro-optic hybrids were

first made possible around 1978, when researchers realised that photons

could respond to electrons through certain media such as lithium niobate

(LiNbO3). To make the thin polymer films for electro-optic applications, NASA

scientists dissolve a monomer (the building block of a polymer) in an organic

solvent. This solution is then put into a growth cell with a quartz window. An

ultraviolet lamp shining through this window creates a chemical reaction,

causing a thin polymer film to deposit on the quartz.

An ultraviolet lamp causes the entire quartz surface to become coated, but

shining a laser through the quartz can cause the polymer to deposit in specific

patterns. Because a laser is a thin beam of focused light, it can be used to

draw exact lines. A laser beam's focus can be as small as a micron-sized spot

(1 micron is 1-millionth of a meter, or 1/25,000 of an inch), so scientists can

deposit the organic materials on the quartz in very sophisticated patterns. By

painting with light, scientists can create optical circuits that may one day

replace the electronics currently used in computers.

NASA scientists are making these organic thin films on the Space Shuttle to

overcome problems caused by convection. Convection is a circular motion in

air or in a liquid created from uneven heating. On Earth's surface, when a gas

or liquid is heated it expands, becoming lighter and less dense. This lighter

material rises, mixing with cooler and denser material from above. Such

turbulence occurs in the world's weather patterns or even in a pot of water

boiling on the stove.

Convection creates difficulties when trying to create a uniform film. A UV lamp

or laser light will raise the temperature of the film solution, causing the hotter

solution to rise. Aggregates of solid polymers often form in the solution, and

convective flows that develop in the solution can carry these aggregates to the

surface of the quartz. Because aggregates on optical films can cause light to

scatter, the goal is to make the films as smooth and uniform as possible.

Convection is actually caused both by heating and the Earth's gravity. The

microgravity conditions of space reduce the effects of convection because

there is no up direction for the heated material to head towards. Any

aggregates in space-produced films can only reach the quartz through the

slower process of diffusion. Because microgravity reduces convection, films

made in space have fewer polymer aggregates than those made on Earth.

Convection causes other problems for the production of optical films.

Convection can affect the distribution of molecules in a fluid, so films created

on Earth can have regions that are rich or poor in certain molecules rather

than evenly dispersed throughout. Films made in microgravity often have

more highly aligned and densely packed molecules than Earth formed films.

Because there is little convection in a microgravity environment, scientists can

produce smoother and more uniform films in space.

The thin films being developed by NASA are composed of organic molecules,

which often are more sensitive than inorganics to changes in light intensity.

Organics can perform a large number of functions such as switching, signal

processing and frequency doubling, all while using less power than inorganic

materials. While silicon and other inorganics are often used in electronic

computer hardware, the all optical computers of the future will probably use

mostly organic parts. There will be a gradual hybridisation in which computers

using both organic and inorganic parts make use of photons and electrons.

These hybrid devices will eventually lead to all optical computer systems.

In the optical computer of the future electronic circuits and wires will be

replaced by a few optical fibers and films, making the systems more efficient

with no interference, more cost effective, lighter and more compact.

Smaller, more compact computers are often faster because computation time

depends on shorter connections between components. In the search for

speed, computer chips have grown ever smaller, it is estimated that the

number of transistor switches that can be put onto a chip doubles every 18

months. It is now possible to fit 300 million transistors on a single silicon chip,

and some scientists have predicted that in the next few decades computer

technology will have reached the atomic level. But more transistors mean the

signals have to travel a greater distance on thinner wires. As the switches and

connecting wires are squeezed closer together, the resulting crosstalk can

inadvertently cause a digital signal to change from a 1 to a 0. Scientists are

working on developing newer, better insulators to combat this problem. But

optical computers wouldn't need better insulators because they don't

experience crosstalk. The thin-films used in electro-optic computers would

eliminate many such problems plaguing electronics today.

The thin films allow us to transmit information using light. And because we're

working with light, we're working with the speed of light without generating as

much heat as electrons. We can move information faster than electronic

circuits, and without the need to remove damaging heat.

Multiple frequencies of light can travel through optical components without

interference, allowing photonic devices to process multiple streams of data

simultaneously. And the optical components permit a much higher data rate

for any one of these streams than electrical conductors. Complex programs

that take 100 to 1,000 hours to process on modern electronic computers could

eventually take an hour or less on photonic computers.

The speed of computers becomes a pressing problem as electronic circuits

reach their maximum limit in network communications. The growth of the

Internet demands faster speeds and larger bandwidths than electronic circuits

can provide. Electronic switching limits network speeds to about 50 gigabits

per second (1 gigabit (Gb) is 1 billion bits).

Terabit speeds are already needed to accommodate the 10 to 15 percent per

month growth rate of the Internet, and the increasing demand for bandwidth-

intensive data such as digital video (1 Tb is 1 trillion bits). All optical switching

using optical materials can relieve the escalating problem of bandwidth

limitations imposed by electronics.

Last year Lucent Technologies' Bell Laboratory introduced technology with

the capacity to carry the entire world's Internet traffic simultaneously over a

single optical cable. Optical computers will someday eliminate the need for the

enormous tangle of wires used in electronic computers today. Optical

computers will be more compact and yet will have faster speeds, larger

bandwidths and more capabilities than modern electronic computers.

Optical components like the thin-films developed by NASA are essential for

the development of these advanced computers. By developing components for

electro-optic hybrids in the present, NASA scientists are helping to make

possible the amazing optical computers that will someday dominate the future.

Near new millennium not only concern over Y2K only those float but facts about future of

the world optimistic computerization. In fact scientists are and also computer experts have

tabulated several aspects computer in the future which will make initiative in the new

millennium. Therefore design have tabulated 10 facets future computer technology.

Computer will own character humanity

Therefore computer will know commands say, virtual presence consumerism (virtual

presence) and attack emotion.

Network would become much more ingenious

Network system will be created has features as faster, smarter home network system, IPV4’s

use, digital line and intra extension with various equipment telecommunications.

1. Web also be smarter Web will also introduce personal portal, XML’s use replace

HTML and search use go through image or QBIC (Query by content image). Small

device thinking own devices like telephone, watch, microwave oven, TV and

refrigerator will become smarter. Use of software as StrongARM, DragonBall and

pSOS will be enhanced.

2. Software be shrewder –

Softwares will use commands say, natural language use, use technology net Neural.

Operating-system software network will also be shrewder as Bayesian able Networks

function by own.

Internet economy will be powerful

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Internet economy will develop rapidly and e-commerce web sites will become one main

agenda in the new millennium. With as many as 180 millions all internet user, future total

spent in Internet is equal AS$41 billion near 2003.

New generation computer

Computer will make visible display XGA’s supper (1,280-by-1,024), Roentgen’s display, a

display 16.3-inci with resolution 2,560 x 2,048 and large and wide display.

Virtual entertainment

More digital many characters realistic can produce. 3D’s technology and SIMD’s flow

Extensions (SSE) will be developed. chat’s column will be held in the form 3D chat. While

in fabrication DirectX’s game 8.0 also would be produced.

Digital identity

Self-information will become more open-ended and independent. End up all personal self-

information could be achieved with easy. While information and transaction in e-commerce

also will be enhanced and this will make feel safe clientele.

Forecast

Near year 2011, microprocessor will use transistor one billion and operate to the speed of

10GHz and use semiconductor process of technology 0.07-micron can do count 100 billion

operation in one second.

Electronic Digital PaperXerox Corporation has announced that it has selected 3M as the manufacturer to bring to market its Electronic Paper, a digital document display with the portability of a plain sheet of paper.

Developed at the Xerox Palo Alto Research Center (PARC), electronic paper represents a new kind of display, falling somewhere between the centuries old technology of paper and a conventional computer screen. Like paper, it is user friendly, thin, lightweight and flexible. But like a computer display, it is also dynamic and rewritable. This combination of properties makes it suitable for a wide range of potential applications, including:

Electronic paper newspapers offering breaking news, incoming sports scores, and up to the minute stock quotes, even as the paper is being read.

Electronic paper magazines that continually update with breaking information and make use of animated images or moving pictures to bring stories to life.

Electronic paper textbooks, which could amalgamate a number of textbooks into one book, allowing students to thumb through the pages, scan the information and mark up pages as they would a regular book.

Electronic paper displays in the form of wall size electronic whiteboards, billboards and portable, fold up displays.

The technology, supported by a portfolio of Xerox patents, has been prototyped at PARC on a limited scale. Xerox' collaboration with 3M establishes a means by which the electronic paper material, essentially the paper pulp of the future can be manufactured in the volumes necessary to meet market demands and make the development of a wide range of supporting applications commercially viable.

In moving from the research laboratory to licensed manufacturing, electronic paper is taking its first step to the commercial market. It will not be long before a single renewable sheet of electronic paper offers a never ending parade of news and information.

How it works

 

Electronic paper utilises a new display technology called a gyricon, invented by Xerox. A gyricon sheet is a thin layer of transparent plastic in which millions of small beads, somewhat like toner particles, are randomly dispersed. The beads, each contained in an oil-filled cavity, are free to rotate within those cavities. The beads are bichromal, with hemispheres of contrasting colour (e.g. black and white), and charged so they exhibit an electrical dipole.

Under the influence of a voltage applied to the surface of the sheet, the beads rotate to present one coloured side or the other to the viewer. A pattern of voltages can be applied to the surface in a bit wise fashion to create images such as text and pictures. The image will persist until new voltage patterns are applied to create new images.

There are many ways an image can be created in electronic paper. For example, sheets can be fed into printer like devices that will erase old images and create new images. Used in these devices, the electronic paper behaves like an infinitely reusable paper substitute.

Although projected to cost somewhat more than a normal piece of paper, a sheet of electronic paper could be reused thousands of times. Printer like devices can be made so compact and inexpensive that you can imagine carrying one in a purse or briefcase at all times. One such envisioned device, called a wand, can be pulled across a sheet of electronic paper by hand to create an image. With a built in input scanner, this wand becomes a hand-operated multi function device, a printer, copier, fax, and scanner all in one.

For applications requiring more rapid and direct electronic update, the gyricon material might be packaged with a simple electrode structure on the surface and used more like a traditional display. An electronic paper display could be very thin and flexible. A collection of these electronic paper displays could be bound into an electronic book. With the appropriate electronics stored in the spine of the book, pages could be updated at will to display different content.

For portable applications, an active matrix array may be used to rapidly update a partial or full page display, much like is used in today's portable devices. The lack of a backlight and eliminated requirement to refresh the display (since it is bistable), along with improved brightness compared to today's reflective displays, will lead to utilisation in lightweight and lower power applications.

Xerox has had significant activity in developing this technology for some time. Although not yet perfected, the technology is currently at the state where it is suitable for development for the first set of applications. They are currently engaging partners in both manufacturing and application areas and see a bright future for this technology.

Holographic Storage Technologies

 

The theory of holography was developed by Dennis Gabor, a Hungarian physicist, in the year 1947. His theory was originally intended to increase the resolving power of electron microscopes. Gabor proved his theory not with an electron beam, but with a light beam. The result was the first hologram ever made. The early holograms were legible but plagued with many imperfections because Gabor did not have the correct light to make crisp clear holograms as we can today . Gabor needed laser Light. In the 1960s two engineers from the University of Michigan: Emmett Leith and Juris Upatnieks, developed a new device which produced a three dimensional image of an object. Building on the discoveries of Gabor, they produced the diffuse light hologram. Today, we can see holograms, or 3D images, on credit cards, magazine covers and in art galleries. Yet this unique method of capturing information with lasers has many more applications in the industrial world and is on the verge of revolutionising data storage technology as we know it.

A project at Lucent Technologies Bell Laboratories could result in the first commercially viable holographic storage system. Leveraging advances across a number of technologies from micromirror arrays to new non linear polymer recording media, the team hopes to spin the project off into a startup. This technology not only offers very high storage densities, it could access that data at very high rates, due to the fact that holographic methods read an entire page of data in one operation. While conventional optical storage techniques read and write data by altering an optical medium on a per bit basis, holographic storage records an entire interference pattern in a single operation. This technique makes unique demands on both the light source and the recording medium. While a conventional optical disk system can get by with a relatively low power laser diode and a single detector, holographic techniques require high quality laser sources and detector arrays. However, these types of components have been getting cheaper. For example, CMOS pixel sensors offer the potential for the low cost detection of data arrays, while digital micromirrors can be used for data input from electronic systems. The biggest challenge has been devising a suitable optical medium for storing the interference patterns. The team turned to non linear polymers in its search for that key component. What is needed is a medium that can support the overlap of megabyte data pages, each with a high enough diffraction efficiency to enable high transfer rates. These two demands sound reasonably simple, but it really leads to a very long list of pretty stringent criteria for what a material has to do. The researchers have found what they believe is a suitable candidate, an acrylic polymer compound that polymerises in response to light. In addition to having the required optical performance properties, the new material, being a polymer, is easy to form into thick films. Film thickness directly relates to storage capacity and inorganic nonlinear materials, which

are crystalline, are difficult to build in thick films. The researchers have built a prototype system using off the shelf components such as camera lenses and digital micromirrors from Texas Instruments.

Many novel technologies are being pursued in parallel towards accomplishing higher capacities per disk and higher data transfer rates. Several unconventional long term optical data storage techniques promise data densities greater than 100 Gb/in2 and perhaps even exceeding Tb/in2. These include near field and solid immersion lens approaches, volumetric (multi layer and holographic) storage, and probe storage techniques.

A solid immersion lens approach using MO media pursued by Terastor in the United States promises at least 100 Gb/in2 areal density. This technique relies on flying a small optical lens about 50 nm above the storage medium to achieve spot sizes smaller than the diffraction limit of light. Since the head is now lighter, this type of technology may lead to access times comparable with hard drives. Several Japanese companies are intrigued by the approach and are involved in Terastor's activities. Similar objectives are pursued by Quinta, a Seagate Company, where increasing amounts of optical technologies including optical fibers and fiber switches are used to reduce the size and weight of the head, which is non flying, but still placed quite near to the disk medium.

Multi layer storage is pursued both in Japan and the United States. In Japan the effort concentrates on increasing the number of storage layers in a PC based DVD disk. Some researchers also envision adapting multi layer recording to MO media by simultaneously reading and computing the data on several layers. Both approaches, however, have limited scalability in the number of layers. In the United States, Call/Recall, Inc. is using a fluorescent disk medium to record and read hundreds of layers. Also in the United States, significant effort is being put into developing holographic storage, aiming for areal densities exceeding 100 Gb/in2. Companies both in the United States and Japan are exploring the use of parallel heads to speed up data transfer rates. Finally, both in Japan and in the United States, optically assisted probe techniques are being explored to achieve areal densities beyond a Tb/in2. In summary, a fast growing removable data storage market governed by optical storage has resulted from substantial progress that has been made in optical disk storage techniques. These advances have come through a combination of laser wavelength reduction, increases in the objective lens numerical aperture, better crosstalk management, and coding improvements under the constant pull of new applications. Undoubtedly, emerging applications will pull optical storage techniques to reach new performance levels. There is room for advances in storage capacity, as transitions to blue lasers, near field optical recording, and multi layer systems will occur.

Solid State Storage Technologies

  

OmniDimensional Systems plans to create a 2 Gigabyte solid state memory by integrating thin film transistors and diodes onto a substrate that is formed from the flexible foil used to store information optically on CD-ROM. The intent is to substitute thin film electronics for the slow and unreliable mechanical parts used in optical drives, enabling subsystems that promise virtually instantaneous access to very large databases.

The company is combining the solid state memory with a special encoding technique that it says can pack three times the normal amount of information into a given space. The company uses the basic data encoding and compression scheme, called autosophy, in its data communications products.

What they've done is marry two mature technologies to fill a need for cheap, large associative memories. Autosophy can do the same thing for rewritable optical memories, by using a secondary grid.

CD-ROM and similar rewritable optical media modify the surface of a thin sheet of foil with various aberrations, which are normally sensed by a photodiode's picking up light from a laser diode on the read head. In the OmniDimensional approach, the read head is replaced with an array of integrated thin film transistors and diodes of the kind used in active matrix liquid crystal displays (LCD). Autosophy encodings simplify the reading electronics by ensuring that only one output row activates at a time.

The company believes the associative operation of the memory will enable autosophy theory to expand from the RAM based telecommunications code it is today to become a mainstream solid state memory technology.

Autosophy theory enables graphical data to be compressed but requires the use of associative memories to do real time lookups of dictionary entries. The process is simpler for serial telecommunications, because the bit stream is artificially divided into 8 bit characters (plus start and stop bits), which can be kept in a dynamically maintained library in RAM.

For instance, autosophy as used in telecommunications only transmits a full set of information once. The second time, only the address of the information is transmitted. But with graphical data which is two dimensional and not neatly divided into characters, autosophy needs associative memories to perform real time lookup in a dictionary of pieces of the image.

As in telecommunications, the first time an image is sent there is no savings, but the second time only the addresses of the tiles from which it is made need

be sent. With premade associative ROM's installed in TVs, perfect error corrected digital HDTV sized images could be sent over ordinary TV channels.

Autosophy permits you to build enormous systems. The larger the memory, the larger the compression with autosophy, even though every item can still be retrieved in nanoseconds. You can play it forward or backward, skip around or just let the memory act like a normal RAM.

The normal RAM mode divides the 64 inputs and outputs from the associative ROM into address and data lines. Then the 32 bit address can be input and 32 bit data retrieved from the ROM merely by ignoring the input data lines and the output address lines. Because of the associative operation, data can be entered, and the memory will retrieve its address.

The autosophy algorithm also enables the memory technology to map automatically around defects in the foil, just as it error corrects in telecommunications systems. The first level of the dictionary comprises the letters of the alphabet, but has expanded the entries in the dictionaries beyond serial data to parallel data with live video

Solid State Storage Technologies

  

OmniDimensional Systems plans to create a 2 Gigabyte solid state memory by integrating thin film transistors and diodes onto a substrate that is formed from the flexible foil used to store information optically on CD-ROM. The intent is to substitute thin film electronics for the slow and unreliable mechanical parts used in optical drives, enabling subsystems that promise virtually instantaneous access to very large databases.

The company is combining the solid state memory with a special encoding technique that it says can pack three times the normal amount of information into a given space. The company uses the basic data encoding and compression scheme, called autosophy, in its data communications products.

What they've done is marry two mature technologies to fill a need for cheap, large associative memories. Autosophy can do the same thing for rewritable optical memories, by using a secondary grid.

CD-ROM and similar rewritable optical media modify the surface of a thin sheet of foil with various aberrations, which are normally sensed by a photodiode's picking up light from a laser diode on the read head. In the OmniDimensional approach, the read head is replaced with an array of integrated thin film transistors and diodes of the kind used in active matrix liquid crystal displays

(LCD). Autosophy encodings simplify the reading electronics by ensuring that only one output row activates at a time.

The company believes the associative operation of the memory will enable autosophy theory to expand from the RAM based telecommunications code it is today to become a mainstream solid state memory technology.

Autosophy theory enables graphical data to be compressed but requires the use of associative memories to do real time lookups of dictionary entries. The process is simpler for serial telecommunications, because the bit stream is artificially divided into 8 bit characters (plus start and stop bits), which can be kept in a dynamically maintained library in RAM.

For instance, autosophy as used in telecommunications only transmits a full set of information once. The second time, only the address of the information is transmitted. But with graphical data which is two dimensional and not neatly divided into characters, autosophy needs associative memories to perform real time lookup in a dictionary of pieces of the image.

As in telecommunications, the first time an image is sent there is no savings, but the second time only the addresses of the tiles from which it is made need be sent. With premade associative ROM's installed in TVs, perfect error corrected digital HDTV sized images could be sent over ordinary TV channels.

Autosophy permits you to build enormous systems. The larger the memory, the larger the compression with autosophy, even though every item can still be retrieved in nanoseconds. You can play it forward or backward, skip around or just let the memory act like a normal RAM.

The normal RAM mode divides the 64 inputs and outputs from the associative ROM into address and data lines. Then the 32 bit address can be input and 32 bit data retrieved from the ROM merely by ignoring the input data lines and the output address lines. Because of the associative operation, data can be entered, and the memory will retrieve its address.

The autosophy algorithm also enables the memory technology to map automatically around defects in the foil, just as it error corrects in telecommunications systems. The first level of the dictionary comprises the letters of the alphabet, but has expanded the entries in the dictionaries beyond serial data to parallel data with live video.

Molecular Switches  

The world of molecular computing, with its ultrafast speeds, low power needs and inexpensive materials, is one step closer to reality. Using chemical processes rather than silicon based photolithography, researchers at Rice

University and Yale University in the US have created a molecular computer switch with the ability to be turned on and off repeatedly.

Such a switch, or logic gate, is a necessary computing component, used to represent ones and zeros, the binary language of digital computing.

As far as building the basic components of molecular computing is concerned, 50 percent of the job is done, the other 50 percent is memory. Rice and Yale researchers plan to announce a molecular memory device soon.

The cost of the molecular switches would be at least several thousand times less expensive than traditional solid state devices. They also promise continued miniaturisation and increased computing power, leapfrogging the limits of silicon.

The switch works by applying a voltage to a 30 nanometer wide self assembled array of the molecules, allowing current to flow in only one direction within the device. The current only flows at a particular voltage, and if that voltage is increased or decreased it turns off again making the switch reversible. In other previous demonstrations of a molecular logic gate there was no reversibility.

In addition the difference in the amount of current that flows in the on/off state, known as the peak to valley ratio is 1000 to 1. The typical silicon device response is at best, 50 to 1. The dramatic response from off to on when the voltage is applied indicates the increased reliability of the signal.

The active electronic compound, 2'-amino-4-ethynylphenyl-4'-ethynylphenyl-5'-nitro-1-benzenethiol, was designed and synthesised at Rice. The molecules are one million times smaller in area than typical silicon-based transistors.

Not only is it much smaller than any switch that you could build in the solid state, it has complementary properties, which in this case if you want a large on/off ratio it blows silicon away.

The measurements of the amount of current passing through a single molecule occurred at a temperature of approximately 60 Kelvin, or about -350 degrees Fahrenheit.

In addition to logic gates, potential applications include a variety of other computing components, such as high frequency oscillators, mixers and multipliers.

It really looks like it will be possible to have hybrid molecular and silicon based computers within five to 10 years.

Quantum

Computers 

Today's powerful computers that run on microscopic transistor chips won't begin to match the speed of a totally different kind of computer which may be available 50 years from now, thanks to researchers at The University of Arizona in Tucson.

We all know that information technology has been driving our economic engine over the past decade or two. But for that to continue, a new paradigm for information processing will be needed by the middle of the next century. It looks like quantum information may be a candidate, there are no fundamental barriers in the way. There is no basic fundamental law that says this cannot be done. Still, it's going to be very hard.

Quantum computing has potential to shatter the entire concept of binary computing, the use of zero's and one's, "on" and "off," to represent information digitally.

Researchers at the University of New Mexico propose a new concept for how individual atoms might be controlled at the very quantum level for computers for the future.

The researchers at the Optical Sciences Center are now about to begin experiments to test their theory that neutral or chargeless atoms, trapped like individual eggs in an egg carton by a lattice created by interfering laser beams and super cooled to the point of zero motion, will work for quantum computing.

Researchers have succeeded in cooling light trapped atoms to the zero point of motion, a pure vibrational state that is the crucial initialisation step to using atoms as quantum information bits. The pure quantum state would be the logical zero for a quantum mechanical computer. The scientists' success at cooling atoms was no small achievement. Atoms in this super cooled state are colder than liquid helium by roughly the same factor that liquid helium is colder than the center of the sun.

The researchers have reported that their scheme for stacking atom filled optical lattices so the neutral atoms will sufficiently interact to make quantum logic operations possible. If the scheme works, the big advantage is that atoms can be easily accessible for laser manipulation but remain isolated from the surrounding environment. Random forces from the outside world that act on the tiny quantum bits is perhaps the greatest problem confronting researchers trying to build a real quantum computer.

In today's computers, transistors store and process information that is coded as a combination of the numbers "1" and "0." The transistors in these classical computers have decreased in size and increased in speed exponentially

during the past decades. But in a couple of decades from now, conventional technology will no longer be able to increase computer performance, scientists predict.

So mathematicians, physicists and computer scientists visualise replacing transistors with single atoms, creating a new kind of computer where information is manipulated according to the laws of quantum physics. A quantum mechanical computer would manipulate information as bits that exist in two states at once.

A classical computer takes one input at a time, does its computation and gives you one answer. A quantum computer, very loosely speaking, allows you to enter all possible inputs at one time and perform all the corresponding computations in parallel. However, this is a very simplistic way of putting it. The laws of quantum physics only allow you to observe one of the many possible outputs each time you run the computer, so you have to be very clever about how you look at the results. Surprisingly, researchers have discovered that several classes of computational problems can be solved in ways that take advantage of quantum parallelism.

Exactly how powerful is this quantum parallelism? A quantum computer would simultaneously carry out a number of computations equal to two to the power of the number of input bits. That is, if you were to feed a modest 100 bits of information into such a computer, the machine would process in parallel two to the power of 100 different inputs, or simultaneously perform a thousand billion billion billion different computations. The higher the number of bits fed into such a computer, the exponentially greater advantage a quantum mechanical computer has over a classical computer.

Computational scientists have proved in theory that a quantum mechanical computer can solve a number of problems conventional computers cannot. At the moment, one of the driving motivations for developing a quantum mechanical computer is that it can be used to crack secret codes and on the flip side, to communicate information more securely. A quantum mechanical computer could crack a code encrypted for security with a 200 bit number, a problem that would take current classical computers the age of the universe to solve. A quantum mechanical computer could also send information that is fundamentally impossible to decode by anyone other than the intended recipient.

It is important to be honest and say that physicists and computational scientists are far from done with the study of quantum information, and it's not really yet known what kinds of problems such computers might do better than a classical computer, and which you won't do any better than can already be done by classical computers.

VLIW Processors  

Very long instruction word (VLIW) ideas came from the parallel microcode way back in computing's earliest days and from the first supercomputers such as the Control Data CDC6600 and IBM 360/91. In the 1970s, many attached array processors and dedicated signal processors used VLIW-like wide instructions in ROM to compute fast Fourier transforms and other algorithms.

The first true VLIW machines were mini supercomputers in the early 1980s from three companies: Multiflow, Culler, and Cydrome. They were not a commercial success. Still, the compiler writing experience from these endeavors didn't go to waste, Hewlett Packard bought Multiflow, and now Josh Fisher (ex Mult iflow) and Bob Rau (ex Cy drome) lead HP's VLIW compiler effort. Trace scheduling and software pipelining, pioneered by Fisher and Rau, respectively, are now central pillars of VLIW compiler technology.

The trailblazing Multiflow 7/300 used two integer ALUs, two floating-point ALUs, and a branch unit (all built from multiple chips). Its 256-bit instruction word contained seven 32-bit operation codes. The integer units could each perform two operations per 130-ns cycle (four in all) for a performance of about 30 integer MIPS. You could also combine 7/300s to build 512 bit and 1024 bit wide machines.

Cydrome's pioneering Cydra 5 also used a 256-bit instruction word, with a special mode that executed each instruction as a sequence of six 40-bit operations. Its compilers could therefore generate a mix of parallel and conventional sequential code.

While both those VLIW machines used multiple chips, some regard Intel's i860 as the first single-chip VLIW. It depends on the compiler rather than on the hardware to sequence operations correctly.

VLIW isn't solely for CPUs. Holland's Philips Semiconductors, another VLIW innovator, recently launched its VLIW TriMedia digital signal processor chip. TriMedia aims at high end applications such as multimedia PCs, videoconferencing, TV set-top boxes, and digital video cameras. The goal is to be fast enough to eliminate the need for a host CPU and cheap enough at $50 to keep total system cost down.

Plastic Displays  

Polyester may be the material of choice for future flat panel displays. Researchers in the U.S. have recently made breakthroughs in developing thin film transistor displays out of polyethylene terephthalate (PET) - a thin, flexible and rugged plastic that you can bend, roll up, fold, or bend into practically any shape you need.

How do you coax a seemingly inflexible, delicate display to perform such acrobatics? The answer is in the roll to roll technique, a process for

manufacturing thin film transistors (TFTs). Conventional TFTs are manufactured onto a rigid glass substrate, but the new technique calls for making the transistors on flexible plastic. In fact plastic displays can be manufactured in much the same way that potato chip bags are produced, in which a giant sheet is spooled onto a machine that prints the packaging and cuts the material into individual chip bags.

In manufacturing displays, the plastic would be spooled through a machine, transistor circuit layers would be deposited onto the material, etching processes would produce patterns to form the pixels, and the display would then be cut to size.

Technical challenges still remain. This type of process of making semiconductors doesn't exist yet. The concept holds promise not only for a new generation of ultralight, flexible displays but also for cost savings. Since manufacturing plants will need to be retooled for the roll to roll process, startup costs will be substantial. But the potential for cost savings in the long run because of cheap plastic and mass production techniques is also significant.

The real technical challenge though, is a matter of heat. In conventional TFT production, temperatures reach up to 350 degrees Celsius, hotter than plastic can withstand without deforming. The Lawrence Livermore group, funded by DARPA's High Definition Systems Project recently built high performance transistors at or below 100 degrees Celsius by using a short burst of light lasting 35 nanoseconds to produce the polycrystalline silicon (polysilicon).

Meanwhile, Philips Semiconductors Lab in Red Hill, Surrey, England, is also making headway in developing plastic displays. Its recipe calls for making polysilicon transistors on plastic by baking the plastic first, so that the heat used in the transistor production process doesn't cause expansion.

Although mass production of plastic displays is five years away, they could be used in all sorts of ways. The applications could include notebook and desktop displays, video game machines, and hand held appliances, as well as displays that don't exist now, for example, wrap around simulators, roll up displays, wearable displays sewn into clothing, and paper thin electronic books and newspapers. E Ink, based in Boston, is currently developing an ultrathin electronic book based on plastic technolog

Roentgen Display Technology

  

IBM Research has developed a display screen that is so precise it’s as clear as the original paper document. The new display is the culmination of a research project code named Roentgen.

The new Active Matrix Liquid Crystal Display (AMLCD) is based on breakthrough research that allowed the IBM team to use aluminum and copper instead of the metals traditionally used in displays, molybdenum and tungsten. Aluminum and copper are better conductors, and make low-cost, higher resolution possible.

Users who need to view large volumes of complex data will benefit from 200 pixels per inch (ppi) high-resolution and high content displays. The new screens are expected to vastly improve digital libraries - databases of scanned images such as those stored by hospitals or insurance companies, and graphic design and electronic publishing applications. The new screens can display six times the information that can currently be shown on a conventional XGA monitor (1024x768 pixels), which reduces the number of times that a user must pan and zoom to find the desired information.

The new display has 6.6 times as many pixels as the XGA (1024x768 pixels), the most common personal computer display, and four times as many pixels as the SXGA (1280x1024 pixels). At 200 ppi, Roentgen’s pixels are finer than those on a typical Cathode-Ray Tube (CRT) monitor, which has between 80 and 100 ppi. A 10 point character on the new display has four times as many pixels as the same character on a CRT monitor, which translates into sharper edges and crisper images. The new display brings advanced technology to today’s computers and applications.

Scientists at IBM Research have worked on AMLCD since the mid 1980's. An early focus of this work was developing techniques to control yield loss in AMLCDs. The results from this work provided IBM scientists with the insight to create highly complex displays.

Another challenge the researchers overcame was to build a graphics adapter capable of handling a display with more than five million pixels. Once this was designed, the team had to write the device drivers necessary to connect it to Windows NT.

IBM has developed AMLCDs with 80, 100, 120,150 and 200 ppi. At each level of development, users continue to see improvements in the screen images. With the improvement from 150 ppi to 200 ppi, kerning - the micro positioning of letters used in typesetting to make words look better improves, the details of letters improve, and the ability to discern small characters is improved. This is particularly useful for reading ideogram based Asian languages. The human eye can detect much smaller size differences than 200 ppi, but achieving these higher resolution technologies is still not cost effective.

IBM’s 200-ppi display was code named for Wilhelm Conrad Roentgen, the German professor who discovered X-rays in 1895. On the evening of November 8, Wilhelm was drawn to a glowing screen on a nearby table. He immediately determined that the fluorescence was caused by invisible rays

originating from the partially evacuated, glass tube he was using to study cathode rays. Surprisingly, the mysterious rays penetrated the opaque black paper wrapped around the tube and the first X-rays were discovered. One of the goals of the 200 ppi project was to see if it was possible to make a display with a resolution high enough to make it suitable for reading X-rays.

The breakthrough that resulted in the Roentgen display builds on a previous display project, code-named Monet, after the famous French impressionist painter. Monet is a 10.5 inch diagonal 150 ppi SXGA.

 

Roentgen Display Specifications

 

200 ppi 16.3 inch Active Matrix Liquid Crystal Display diagonal viewing area

2560x2048 pixels (5,242,880 full colour pixels) Sub-pixels are 42 x 126 microns 15,728,640 transistors 1.64 miles of thin film wiring on the display Aperture ratio of 27.3% Backlight power of 44 Watts The smallest feature is 5 microns The prototype is 21 inches high and 16.5 inches wide, the total depth

(including base) is 9.5 inches, the thickness of the display is 2.5 inches The weight is approximately 20 pounds The power dissipated by the new display is similar to the power used by

an 18-inch CRT display.

The Roentgen technology will create a new market for LCD's. Industries that heavily rely on paper or film, such as radiology, medical, digital photography and publishing, will be able to process information digitally without sacrificing data and image quality. The display will also be suitable for the financial market. IBM's research indicates that people can read faster with a higher resolution display. The Roentgen will enable dealers, brokers and other financial professionals to obtain information much faster than before

Augmented Reality 

To date, personal computers have not lived up to their name. Most machines sit on the desk and interact with their owners for only a small fraction of the day. Smaller and faster notebook computers have made mobility less of an issue, but the same staid user paradigm persists. Wearable computing hopes to shatter this myth of how a computer should be used. A person's computer should be worn, much as eyeglasses or clothing are worn, and interact with the user based on the context of the situation. With heads up displays, unobtrusive input devices, personal wireless local area networks and a host of other context sensing and communication tools, the wearable computer can act as an intelligent assistant, whether it be through augmented reality, or intellectual collectives.

Augmented reality (AR) is a technology in which a user's view of the real world is enhanced or augmented with additional information generated from a computer model. The enhancement may consist of virtual artifacts to be fitted into the environment, or a display of non-geometric information about existing real objects. AR allows a user to work with and examine real 3D objects, while receiving additional information about those objects or the task at hand. By exploiting people's visual and spatial skills, AR brings information into the user's real world. That is, AR allows the user to stay in touch with the real environment. This is in contrast to virtual reality (VR) in which the user is completely immersed in an artificial world and cut off from the real world. In VR systems, there is no way for the user to interact with objects in the real world. Using AR technology, users can thus interact with a mixed virtual and real world in a natural way. AR systems bring the computer to the user's real work environment, whereas VR systems try to bring the world into the user's computer. This paradigm for user interaction and information visualisation constitutes the core of a very promising new technology for many applications.

However, real applications impose very strong demands on AR technology that cannot yet be met. Some of such demands are listed below. In order to combine real and virtual worlds seamlessly so that the virtual objects align well with the real ones, we need very precise models of the user's environment and how it is sensed. It is essential to determine the location and the optical properties of the viewer (or camera) and the display, i.e. we need to calibrate all devices, combine all the local coordinate systems centered on the devices and objects in the scene in a global coordinate system, register models of all 3D objects of interest with their counterparts in the scene, and track them over time when the user moves and interacts with the scene. Realistic merging of virtual objects with a real scene requires that objects behave in physically plausible manners when they are manipulated, i.e. they occlude or are occluded by real objects, they are not able to move through other objects, and they are shadowed or indirectly illuminated by other objects while also casting shadows themselves. To enforce such physical interaction constraints

between real and virtual objects, the AR system needs to have a very detailed description of the physical scene. There may be many useful applications of this technology. Just as the personal computer has changed the daily routine of the average office worker, computer technology will, in the future, very likely create even more dramatic changes in the construction, design and manufacturing industries. In order to get some idea of what this change will entail, let us examine how a typical construction worker may do his job in the future.

Augmented Reality Applications

 

Mechanical Repair & Training: An engineer with some form of trackable, head mounted display and a see through visor can proceed with his work while seeing a continually updated, annotated display which assists him in identifying the components before him and reminds him of the tasks he must perform.

By simply putting three distinctive marks at known distances from each other, a wearable camera with known focal length can recover the 3D location of the plane defined by these three marks. By extrapolation from an on line technical manual, the rest of the object's 3D location can be derived. Thus, when a repair technician walks up to a broken machine, the machine can transmit its diagnostics to the technician's wearable. The wearable automatically determines the problem, locates the 3D position of the object, and overlays specific 3D real time step by step guidelines on the object for the technician to follow.

Interior Design and Modeling: An interior architect designs, remodels, and visualises a room, using furniture models from a database that are superimposed on video images of the room.

Computer Aided Surgery: A doctor performs surgery using Augmented Reality tools to see medical image data (including volume rendered versions and

computer graphics renderings of physical implants or other devices) visually superimposed on a human subject.

Electric Manufacturing and Diagnostics of Printed Circuit Boards: A technician diagnoses what is wrong with a particular printed circuit board (PC board), using Augmented Reality and Artificial Intelligence technology to analyse the reported symptoms, highlight the detected trouble spots in a video image of the PC board, and overlay relevant information that is pulled out of user manuals.

Apparel Retail: A customer shops for clothes, using an augmented reality system to look through an extensive electronic catalogue and electronically "wear" selected items to see how they fit.

Industrial Plant Maintenance: Maintenance personnel try to find a pipe with a certain functionality among the jungle of existing pipes. The technician sees an adjustable video image of the factory floor on a monitor. Functional data (e.g. labels, measurements such as temperature and pressure) are superimposed on the image to help him identify and inspect the correct pipe.

Road Repair and Maintenance: A repair crew is about to dig a road and wants to avoid hitting major water pipes. The workers aim a camera to the road and get an image of where the main water pipes under the road are. This is accomplished with the aid of an augmented reality system which uses a GPS system and a database of the water pipes in the city.

Navigation: The Global Position System (GPS) allows private users to find their position anywhere on the globe to within 100 meters. Naturally, hooking a GPS system to a wearable computer and mapping software allows the user to track himself while exploring a city. However, the resolution is not fine enough in many situations. By using optical flow (comparing consecutive images to determine the direction of motion) not only can the movement of a user's head be tracked, but also warnings can be given of approaching objects for the visually disabled. By implementing local beacons or a dead reckoning system in the workplace, much more advanced applications can be developed. Examples include virtual museum tour guides, automatic wiring and gas line view overlays in buildings and on streets, and a new computing environment called the reality metaphor. The reality metaphor replaces the typical computer desktop metaphor by overlaying files onto real world objects. Thus, a filing cabinet may have a searchable index overlaid on it. Telephones may have virtual phone directories attached. Virtual 3D post it notes and movies may be applied to objects. Recent electronic mail messages may be rendered on a co-worker's door (or the co-worker) to remind the user of the last communication with that person. Again, such a system would help provide context based information in a timely fashion

Neural Networks  

Artificial neural networks (ANNs) are computational paradigms which implement simplified models of their biological counterparts, biological neural networks. Biological neural networks are the local assemblages of neurons and their dendritic connections that form the (human) brain. Accordingly, artificial neural networks are characterised by

Local processing in artificial neurons (processing elements) Massively parallel processing, implemented by rich connection pattern

between processing elements The ability to acquire knowledge via learning from experience Knowledge storage in distributed memory, the synaptic processing

elements connections

The attempt of implementing neural networks for brain like computations like patterns recognition, decisions making, motor control and many others is made possible by the advent of large scale computers in the late 1950's. Indeed artificial neural networks can be viewed as a major new approach to computational methodology since the introduction of digital computers.

Although the initial intent of artificial neural networks was to explore and reproduce human information processing tasks such as speech, vision, and knowledge processing, artificial neural networks also demonstrated their superior capability for classification and function approximation problems. This has great potential for solving complex problems such as systems control, data compression, optimisation problems, pattern recognition, and system identification.

Artificial neural networks were originally developed as tools for the exploration and reproduction of human information processing tasks such as speech, vision, touch, knowledge processing and motor control. Today, most research is directed towards the development of artificial neural networks for applications such as data compression, optimisation, pattern matching, system modeling, function approximation, and control. One of the application areas to which artificial neural networks are applied is flight control. Artificial neural networks give control systems a variety of advanced capabilities.

Since artificial neural networks are highly parallel systems, conventional computers are unsuited for neural network algorithms. Special purpose computational hardware has been constructed to efficiently implement artificial neural networks. Accurate Automation has developed a Neural Network Processor. This hardware will allow us to run even the most complex neural networks in real time. The neural network processor is capable of multiprocessor operation in Multiple Instruction Multiple Data (MIMD) fashion. It is the most advanced digital neural network hardware in existence. Each neural network processor system is capable of implementing 8000 neurons with 32,000 interconnections per processor. The computational capability of a single processor 140 million connections per second. An 8 processor neural network processor would be capable of over one billion connections per second. The neural network processor architecture is extremely flexible and any neuron is capable of interconnecting with other neuron in the system.

Conventional computers rely on programs that solve a problem using a predetermined series of steps, called algorithms. These programs are controlled by a single, complex central processing unit, and store information at specific locations in memory. Artificial neural networks use highly distributed representations and transformations that operate in parallel, have distributed control through many highly interconnected neurons, and store their information in variable strength connections called synapses.

There are many different ways in which people refer to the same type of neural networks technology. Neural networks are described as connectionist systems, because of the connections between individual processing nodes. They are sometimes called adaptive systems, because the values of these connections can change so that the neural network performs more effectively. They are also sometimes called parallel distributed processing systems, which emphasise the way in which the many nodes or neurons in a neural network operate in parallel. The theory that inspires neural network systems is drawn from many disciplines, primarily from neuroscience, engineering, and computer science, but also from psychology, mathematics, physics, and linguistics. These sciences are working toward the common goal of building intelligent systems

Letizia The Computer Avatar

  

Letizia is a user interface agent that assists a user browsing the World Wide Web. As the user operates a conventional Web browser such as Netscape or Internet Explorer, the agent tracks user behaviour and attempts to anticipate items of interest by doing concurrent, autonomous exploration of links from the user's current position. The agent automates a browsing strategy consisting of a best first search augmented by heuristics inferring user interest from browsing behaviour.

The recent explosive growth of the World Wide Web and other on line information sources has made critical the need for some sort of intelligent assistance to a user who is browsing for interesting information.

Past solutions have included automated searching programs such as WAIS or Web crawlers that respond to explicit user queries. Among the problems of such solutions are that the user must explicitly decide to invoke them, interrupting the normal browsing process, and the user must remain idle waiting for the search results.

The agent tracks the user's browsing behaviour following links, initiating searches, requests for help and tries to anticipate what items may be of interest to the user. It uses a simple set of heuristics to model what the user's

browsing behaviour might be. Upon request, it can display a page containing its current recommendations, which the user can choose either to follow or to return to the conventional browsing activity.

 

Interleaving Browsing With Automated Search

 

The model adopted by Letizia is that the search for information is a cooperative venture between the human user and an intelligent software agent. Letizia and the user both browse the same search space of linked Web documents, looking for interesting documents. No goals are predefined in advance. The difference between the user's search and Letizia's is that the user's search has a reliable static evaluation function, but that Letizia can explore search alternatives faster than the user can. Letizia uses the past behaviour of the user to anticipate a rough approximation of the user's interests.

Critical to Letizia's design is its control structure, in which the user can manually browse documents and conduct searches, without interruption from Letizia. Letizia's role during user interaction is merely to observe and make inferences from observation of the user's actions that will be relevant to future requests.

In parallel with the user's browsing, Letizia conducts a resource limited search to anticipate the possible future needs of the user. At any time, the user may request a set of recommendations from Letizia based on the current state of the user's browsing and Letizia's search. Such recommendations are dynamically recomputed when anything changes or at the user's request.

Letizia is in the tradition of behaviour based interface agents. Rather than rely on a preprogrammed knowledge representation structure to make decisions, the knowledge about the domain is incrementally acquired as a result of inferences from the user's concrete actions.

Letizia adopts a strategy that is midway between the conventional perspectives of information retrieval and information filtering. Information retrieval suggests the image of a user actively querying a base of mostly irrelevant knowledge in the hopes of extracting a small amount of relevant material. Information filtering paints the user as the passive target of a stream of mostly relevant material, where the task is to remove or de-emphasise less relevant material. Letizia can interleave both retrieval and filtering behaviour initiated either by the user or by the agent.

 

Modelling The User's Browsing Process

 

The user's browsing process is typically to examine the current HTML document in the Web browser, decide which, if any, links to follow, or to return to a document previously encountered in the history, or to return to a document explicitly recorded in a hot list, or to add the current document to the hot list.

The goal of the Letizia agent is to automatically perform some of the exploration that the user would have done while the user is browsing these or other documents, and to evaluate the results from what it can determine to be the user's perspective. Upon request, Letizia provides recommendations for further action on the user's part, usually in the form of following links to other documents.

Letizia's leverage comes from overlapping search and evaluation with the idle time during which the user is reading a document. Since the user is almost always a better judge of the relevance of a document than the system, it is usually not worth making the user wait for the result of an automated retrieval if that would interrupt the browsing process. The best use of Letizia's recommendations is when the user is unsure of what to do next. Letizia never takes control of the user interface, but just provides suggestions.

Because Letizia can assume to be operating in a situation where the user has invited its assistance, its simulation of the user's intent need not be extremely accurate for it to be useful. Its guesses only need be better than no guess at all, and so even weak heuristics can be employed.

 

Inferences From The User's Browsing Behaviour

 

Observation of the user's browsing behaviour can tell the system much about the user's interests. Each of these heuristics is weak by itself, but each can contribute to a judgment about the document's interest.

One of the strongest behaviours is for the user to save a reference to a document, explicitly indicating interest. Following a link can indicate one of several things. First, the decision to follow a link can indicate interest in the topic of the link. However, because the user does not know what is referenced by the link at the time the decision to follow it has been made, that indication of interest is tentative, at best. If the user returns immediately without having either saved the target document, or followed further links, an indication of disinterest can be assumed. Letizia saves the user considerable time that would be wasted exploring those dead end links.

Following a link is, however, a good indicator of interest in the document containing the link. Pages that contain lots of links that the user finds worth following are interesting. Repeatedly returning to a document also connotes interest, as would spending a lot of time browsing it relative to its length.

Since there is a tendency to browse links in a top to bottom, left to right manner, a link that has been passed over can be assumed to be less interesting. A link is passed over if it remains unchosen while the user chooses other links that appear later in the document. Later choice of that link can reverse the indication.

Letizia does not have natural language understanding capability, so its content model of a document is simply as a list of keywords. Partial natural language capabilities that can extract some grammatical and semantic information quickly, even though they do not perform full natural language understanding could greatly improve its accuracy.

Letizia uses an extensible object oriented architecture to facilitate the incorporation of new heuristics to determine interest in a document, dependent on the user's actions, history, and the current interactive context as well as the content of the document.

An important aspect of Letizia's judgement of interest in a document is that it is not trying to determine some measure of how interesting the document is in the abstract, but instead, a preference ordering of interest among a set of links. If almost every link is found to have high interest, then an agent that recommends them all isn't much help, and if very few links are interesting, then the agent's recommendation isn't of much consequence. At each moment, the primary problem the user is faced with in the browser interface is which link should I choose next?, And so it is Letizia's job to recommend which of the several possibilities available is most likely to satisfy the user. Letizia sets as its goal to recommend a certain percentage settable by the user of the links currently available.

An Example

 

In the example, the user starts out by browsing home pages for various general topics such as artificial intelligence. The user is particularly interested in topics involving agents, so he or she zeros in on pages that treat that topic. Many pages will have the word agent in the name, the user may search for the word agent in a search engine, and so the system can infer an interest in the topic of agents from the browsing behaviour.

At a later time, the user is browsing personal home pages, perhaps reached through an entirely different route. A personal home page for an author may contain a list of that author's publications. As the user is browsing through some of the publications, Letizia can concurrently be scanning the list of publications to find which ones may have relevance to a topic for which interest was previously inferred, in this case the topic Agents. Those papers in the publication list dealing with agents are suggested by Letizia.

Letizia can also explain why it has chosen that document. In many instances, this represents not the only reason for having chosen it, but it selects one of the stronger reasons to establish plausibility. In this case, it noticed a keyword

from a previous exploration, and in the other case, a comparison was made to a document that also appeared in the list returned by the bibliography search.

 

Persistence Of Interest

 

One of the most compelling reasons to adopt a Letizia like agent is the phenomenon of persistence of interest. When the user indicates interest by following a link or performing a search on a keyword, their interest in that topic rarely ends with the returning of results for that particular search.

Although the user typically continues to be interested in the topic, he or she often cannot take the time to restate interest at every opportunity, when another link or search opportunity arises with the same or related subject. Thus the agent serves the role of remembering and looking out for interests that were expressed with past actions.

Persistence of interest is also valuable in capturing users preferred personal strategies for finding information. Many Web nodes have both subject oriented and person oriented indices. The Web page for a university or company department typically contains links to the major topics of the department's activity, and also links to the home pages of the department's personnel. A particular piece of work may be linked to by both the subject and the author.

Some users may habitually prefer to trace through personal links rather than subject links, because they may already have friends in the organisation or in the field, or just because they may be more socially oriented in general. An agent such as Letizia picks up such preferences, through references to links labelled as people, or through noticing particular names that may appear again and again in different, though related, contexts.

Indications of interest probably ought to have a factor of decaying over time so that the agent does not get clogged with searching for interests that may indeed have fallen from the user's attention. Some actions may have been highly dependent upon the local context, and should be forgotten unless they are reinforced by more recent action. Another heuristic for forgetting is to discount suggestions that were formulated very far in distance from the present position, measured in number of web links from the original point of discovery.

Further, persistence of interest is important in uncovering serendipitous connections, which is a major goal of information browsing. While searching for one topic, one might accidentally uncover information of tremendous interest on another, seemingly unrelated, topic. This happens surprisingly often, partly because seemingly unrelated topics are often related through non obvious connections. An important role for the agent to play is in constantly being available to notice such connections and bring them to the user's attention.

Search Strategies

 

The interface structure of many Web browsers encourages depth first search, since every time one descends a level the choices at the next lower level are immediately displayed. One must return to the containing document to explore brother links at the same level, a two step process in the interface. When the user is exploring in a relatively undirected fashion, the tendency is to continue to explore downward links in a depth first fashion. After a while, the user finds him or herself very deep in a stack of previously chosen documents, and especially in the absence of much visual representation of the context this leads to a lost in hyperspace feeling.

The depth first orientation is unfortunate, as much information of interest to users is typically embedded rather shallowly in the Web hierarchy. Letizia compensates for this by employing a breadth first search. It achieves utility in part by reminding users of neighbouring links that might escape notice. It makes user exploration more efficient by automatically hiding many of the deadend links that waste a users time.

The depth of Letizia's search is also limited in practice by the effects of user interaction. Web pages tend to be of relatively similar size in terms of amount of text and number of links per page, and users tend to move from one Web node to another at relatively constant intervals. Each user movement immediately refocuses the search, which prevents it from getting too far afield.

The search is still potentially combinatorially explosive, so a resource limitation is placed on search activity. This limit is expressed as a maximum number of accesses to non local Web nodes per minute. After that number is reached, Letizia remains quiescent until the next user initiated interaction.

Letizia will not initiate further searches when it reaches a page that contains a search form, even though it could benefit enormously by doing so, in part because there is as yet no agreed upon Web convention for time bounding the search effort. Letizia will, however recommend that a user go to a page containing a search form.

In practice, the pacing of user interaction and Letizia's internal processing time tends to keep resource consumption manageable. Like all autonomous Web searching robots, there exists the potential for overloading the net with robot generated communication activity.

 

Related Work

 

Work on intelligent agents for information browsing is still in its infancy. Letizia differs in that it does not require the user to state a goal at the outset, instead trying to infer goals from the user's browsing behaviour.

Automated Web crawlers have neither the knowledge based approach nor the interactive learning approach. They use more conventional search and indexing techniques. They tend to assume a more conventional question and answer interface mode, where the user delegates a task to the agent, and then waits for the result. They don't have any provision for making use of concurrent browsing activity or learning from the user's browsing behaviour

Future User Interfaces  

Several new user interface technologies and interaction principles seem to define a new generation of user interfaces that will move off the flat screen and into the physical world to some extent. Many of these next generation interfaces will not have the user control the computer through commands, but will have the computer adapt the dialogue to the user's needs based on its inferences from observing the user.

Most current user interfaces are fairly similar and belong to one of two common types: Either the traditional alphanumeric full screen terminals with a keyboard and function keys, or the more modern WIMP workstations with windows, icons, menus, and a pointing device. In fact, most new user interfaces released after 1983 have been remarkably similar. In contrast, the next generation of user interfaces may move beyond the standard WIMP paradigm to involve elements like virtual realities, head mounted displays, sound and speech, pen and gesture recognition, animation and multimedia, limited artificial intelligence, and highly portable computers with cellular or other wireless communication capabilities. It is hard to envision the use of this hodgepodge of technologies in a single, unified user interface design, and indeed, it may be one of the defining characteristics of the next generation user interfaces that they abandon the principle of conforming to a canonical interface style and instead become more radically tailored to the requirements of individual tasks.

The fundamental technological trends leading to the emergence of several experimental and some commercial systems approaching next generation capabilities certainly include the well known phenomena that CPU speed, memory storage capacity, and communications bandwidth all increase exponentially with time, often doubling in as little as two years. In a few years, personal computers will be so powerful that they will be able to support very fancy user interfaces, and these interfaces will also be necessary if we are to extend the use of computers to larger numbers than the mostly penetrated markets of office workers.

Traditional user interfaces were function oriented, the user accessed whatever the system could do by specifying functions first and then their arguments. For example, to delete a file in a line-oriented system, the user would first issue the delete command in some way such as typing delete. The user would then further specify that the name of the item to be deleted. The typical syntax for function oriented interfaces was a verb noun syntax.

In contrast, modern graphical user interfaces are object oriented, the user first accesses the object of interest and then modifies it by operating upon it. There are several reasons for going with an object oriented interface approach for graphical user interfaces. One is the desire to continuously depict the objects of interest to the user to allow direct manipulation. Icons are good at depicting objects but often poor at depicting actions, leading objects to dominate the visual interface. Furthermore, the object oriented approach implies the use of a noun verb syntax, where the file is deleted by first selecting the file and then issuing the delete command (for example by dragging it into the recycle bin). With this syntax, the computer has knowledge of the operand at the time where the user tries to select the operator, and it can therefore help the user select a function that is appropriate for that object by only showing valid commands in menus and such. This eliminates an entire category of syntax errors due to mismatches between operator and operand.

A further functionality access change is likely to occur on a macro level in the move from application oriented to document oriented systems. Traditional operating systems have been based on the notion of applications that were used by the user one at a time. Even window systems and other attempts at application integration typically forced the user to use one application at a time, even though other applications were running in the background. Also, any given document or data file was only operated on by one application at a time. Some systems allow the construction of pipelines connecting multiple applications, but even these systems still basically have the applications act sequentially on the data.

The application model is constraining to users who have integrated tasks that require multiple applications to solve. Approaches to alleviate this mismatch in the past have included integrated software and composite editors that could deal with multiple data types in a single document. No single program is likely to satisfy all computer users, however, no matter how tightly integrated it is, so other approaches have also been invented to break the application barrier. Cut and paste mechanisms have been available for several years to allow the inclusion of data from one application in a document belonging to another

application. Recent systems even allow live links back to the original application such that changes in the original data can be reflected in the copy in the new document (such as Microsoft`s OLE technology). However, these mechanisms are still constrained by the basic application model that require each document to belong to a specific application at any given time.

An alternative model is emerging in object oriented operating systems where the basic object of interest is the user's document. Any given document can contain sub objects of many different types, and the system will take care of activating the appropriate code to display, print, edit, or email these data types as required. The main difference is that the user no longer needs to think in terms of running applications, since the data knows how to integrate the available functionality in the system. In some sense, such an object oriented system is the ultimate composite editor, but the difference compared to traditional, tightly integrated multi-media editors is that the system is open and allows plug and play addition of new or upgraded functionality as the user desires without changing the rest of the system.

Even the document oriented systems may not have broken sufficiently with the past to achieve a sufficient match with the users' task requirements. It is possible that the very notion of files and a file system is outdated and should be replaced with a generalised notion of an information space with interlinked information objects in a hypertext manner. As personal computers get multi Gigabyte harddisks, and additional Terabytes become available over the Internet, users will need to access hundreds of thousands or even millions of information objects. To cope with this mass of information, users will need to think of them in more flexible ways than simply as files, and information retrieval facilities need to be made available on several different levels of granularity to allow users to find and manipulate associations between their data. In addition to hypertext and information retrieval, research approaching this next generation data paradigm includes the concept of piles of loosely structured information objects, the information workspace with multiple levels of information storage connected by animated computer graphics to induce a feeling of continuity, personal information management systems where information is organised according to the time it was accessed by the individual user, and the integration of fisheye hierarchical views of an information space with feedback from user queries. Also, several commercial products are already available to add full text search capabilities to existing file systems, but these utility programs are typically not integrated with the general file user interface

The 3D Graphical User Interface

  

The interface environment is a fashionable phrase right now, but it's worth pointing out that we're really talking about two types of environments here: one is the metaphoric 3D space conjured up on the screen, with its avatars and texture mapping, the other is the real estate of real offices, populated by real people.

Is a VRML style 3D interface likely to improve any day to day productivity applications? Aren't there cases where 3D metaphors confuse more than they clarify? If so, will future users feel comfortable hopping back and forth between 2D and 3D environments over the course of an average workday? Are DOOM and Quake the killer apps of the 3D interface, or is there something more enriching lurking around the corner?

Most new technologies start out declared as the answer to every problem. Then, people find out what pieces of the world's problem they actually solve and they quietly take their place among the other solutions. For example, microwave ovens were heralded as replacements for every appliance in your kitchen.

Instead, microwave ovens became yet another tool in the kitchen. Microwave ovens became indispensable as a minor adjunct to primary cooking processes taking place somewhere else.

Similarly, 3D, along with handwriting, gesture, and voice recognition, will take its place as one technology among many, there to perform whatever large or small measure of an overall activity may be needed.

An area of 3D that has not yet been fully appreciated is the illusion of depth that can be generated on a normal, 2D screen. Xerox PARC has a cone tree allowing rapid document retrieval. MIT Media Lab has interesting infinite spaces within a finite boundary 3D worlds for document retrieval.

3D on screens will not work well until we drastically improve resolution. Sun Microsystems has built a 3D camera that can feed onto a 2D screen. Users wearing shutter glasses would then see a 3D image that would move vantage point as the user moved in space before the screen.

The only way we can achieve enough depth on our display to enable users to explore the depths of a 3D image, with or without shutter glasses, is to drastically increase the resolution of our screens. 300 dpi is a start. 2400 to 4800 is what is needed.

Which brings us to VRML, it doesn't work, and it won't work until the resolution is drastically improved. Sun Microsystems has built a VR room with three high resolution projectors throwing millions of pixels on three screens that wrap around you. The resolution is close to approaching adequate. The resolution in head mounted displays is very poor, and it will be for a long time to come.

People flipping back and forth between 2D and 3D graphic designs on 2D screens will occur not over the course of an average working day, but over the

course of an average working minute. People will also adopt and adapt to simple hand held 3D devices, even if they must wear light weight shutter glasses to use them. People will not walk around the office wearing head mounted displays. Mainstream VRML is a long way away.

When does 3D fail us? When it's misused to represent documents. It's understandable that we'd first want to use 3D as a front end to our document spaces, after all, document spaces are the bedrock of the 2D GUI's. But try reading a textual document in a 3D space, it's almost impossible. You need to face it head on, get close enough, and probably pitch your head up and down to get all the text. That is the misuse of a powerful tool, trying to adapt it backward into a preexisting paradigm, rather than jumping forward into a new one.

On the other hand, if you're trying to understand the relations between a set of documents, considering such metadata as age, size, creator, geographical region of interest, language, specific subject being covered you can see that very soon we'd exhaust the limits of representability within a 2D GUI, and would have to resort to some pretty fancy tricks used by both the Windows 95 and Macintosh desktops to tame this chaotic sea of metadata complexity. Already the desktop metaphor is breaking down, precisely because it was designed around a document centric view of the world.

But the World Wide Web isn't just a swirling sea of documents. It's an active space which conforms itself to requests made of it, a far cry from a database of documents.

The Internet is not a plug in. And the desktop is not reaching out to the Internet, rather, the Internet is reaching out to the desktop. But the desktop can't cope with the scope of this transformation, furthermore it's unrealistic to think that it should. In fact the Internet confronts us with a riot of information, and right now 3D interfaces are the best hope for interfaces which can "tame" the information overload.

It is necessary to realise that the navigation of VRML worlds is moving us in a direction, based on a need for different points of view of solid spaces and objects. It seems that from the cognitive research, people use the extra z axis, forward and back, for remembering where objects are placed around their work surfaces, as well as in x laterally and for a limited range of y. As we walk around our office environments we use the z dimension to move into additional spaces, but there is little relative change in our y axis knowledge (height). What is critical is to limit the users options somehow to avoid additional axes of control confusion, encountered in real flight from six degrees of control. We still need to do some quality perceptual cognitive research in this domain. The ability to provide true 3-D or stereo perspectives is still computationally and hardware limiting.

We will also see more interfaces use concepts such as layering or overlapping transparency, which has been termed 2.5 D, as seen in MITs spatial data based management system in the 70s. Current work at the Media Lab in the Visual Language workshop has started to show great promise in applications of

transparency and focus pull for navigating libraries of data sets. The smoothness and speed of response of these systems shows the hope for systems such as VRML, when we have more computational power available on set top boxes. Clearly the use of 3D is much clearer when we know there is some inherent 3Dness to the data. Exploring geographical data is much easier given the known 3D world metaphor, moving over body data is made clear when using a real 3D body, and then there is the presentation of 3-n D data across time. Animation is a useful tool to show data relationships, but additional axis of display representation can facilitate the understanding of their interrelationships too. It depends on the types of data being displayed, and the users task as to whether additional axes show any real benefit in performance or learning.

Applications that make the best use of 3D need more time to develop. At the moment there is very limited special purpose uses only for 3D. Sometimes designers use 3D either for feature appeal, or as an excuse for poor design when they cannot think of a 2D solution. With a new generation of game playing kids, the controls over 3D spaces will possibly be needed to keep interest high in work applications. The limitation of the flat existing metaphors is somewhat constrained by the current I/O devices. The pervasiveness of the keyboard will be limited to work processing activities, and will change when we think of a computer as being more than a heavy box shaped screen that we sit at everyday. The keyboard does not have a place in the living room, which will make it take alternate form factors along with the navigational control over n dimensional custom spaces.

Manipulation of 3D spaces and 3D objects isn't easy with just a mouse and keyboard, and will need new hardware inputs to become commonplace before people can effortlessly control themselves and objects in 3D spaces.

Certainly, though, 3D offers a tremendous new opportunity for the creation of entirely new editorial content, and so it will become prevalent in the environment quickly. As the obvious follow on to integrating linear textual works and planar graphical pieces of art we'll create whole populated worlds. 3D objects will be widely used within the growing desktop metaphor given a great rendering engine, we can create super rich entities that are cheap to download because the author just provides the instructions to create them

Machine Translation  

Serious efforts to develop machine translation systems were under way soon after the ENIAC was built in 1946, and the first known public trial took place in January 1954 at Georgetown University. We've made remarkable progress in the past fifty years, but machine translation involves so many complex tasks that current systems give only a rough idea or indication of the topic and content of the source document. These systems tend to reach a quality barrier beyond which they cannot go, and work best if the subject matter is specific or

restricted, free of ambiguities and straightforward, the typical example for this type of text are computer manuals. We'll need more advanced systems to handle the ambiguities and inconsistencies of the real world languages, no wonder that translation, whether performed by machine or by human, is often regarded as an art discipline, and not as an exact science.

Today we have an entire range of translation methods with varying degrees of human involvement. Two extreme ends of the translation spectrum are fully automatic high quality translation which has no human involvement and traditional human translation which has no machine translation input. Human aided machine translation and machine aided human translation lie in between these extremities, with human aided machine translation being primarily a machine translation system that requires human aid, whereas machine aided human translation is a human translation method that is utilising machine translation as an aid or tool for translation. The term Computer Assisted Translation is often used to represent both human aided machine translation and machine aided human translation.

So, what's so hard about machine translation? There's no such thing as a perfect translation, even when performed by a human expert. A variety of approaches to machine translation exist today, with direct translation being the oldest and most basic one of them. It translates texts by replacing source language words with target language words, with the amount of analysis varying from system to system. Typically it would contain the correspondence lexicon, lists of source language patterns and phrases and mappings to their target language equivalents. The quality of the translated text will vary depending on a size of the system's lexicon and on how smart the replacement strategies are. The main problem with this approach is its lack of contextual accuracy and the inability to capture the real meaning of the source text.

Going a step further, syntactic transfer systems use software parsers to analyse the source-language sentences and apply linguistic and lexical rules (or transfer rules) to rewrite the original parse tree so it obeys the syntax of the target language. On the other hand, interlingual systems translate texts using a central data representation notation called an interlingua. This representation is neutral to any languages in the system and breaks the direct relationship that a bilingual dictionary approach would have. Statistical systems use standard methods for translation, but their correspondence lexicon are constructed automatically, using advanced alignment algorithms from a large amount of text for each language, usually available in online databases

HotVideo Multimedia Interface

  

Information at the touch of a button. That’s what the Internet gives you. Going from Web site to home page to in depth information has been possible due to the use of hypertext, which indicates links to related screens. With the onslaught of videos and graphics on the Internet, hypervideo was the natural next step. Now, IBM Research has a new technology that takes the connection even further.

Hot Video is an innovative implementation of hypervideo. It extends the concept of hyper links from text and images to any dynamic object within a video. With HotVideo, sections of a digital video can be linked to various locations, such as home pages, other video clips, audio clips, images, text or executables. HotVideo transforms the two dimensional space of ordinary videos into true multimedia information space.

The video source for HotVideo can reside in disks, DVD`s, server files or from a web server over the Internet. When a video is played, HotVideo synchronises data that resides in different files. Since the information is stored separately, the video itself never changes. What appears is an indicator that highlights a hot link location. A green indicator means there is no link. When the indicator turns red, it means there is a hot link. Hot Video is not intrusive, the user can either connect to another location, or continue to view the video.

HotVideo includes a highly flexible authoring tool that enables users to customise the look of their hot links and even the way the interface works. For example, a colour or highlighting change can be set up so that it is revealed on demand by the user by clicking on the right mouse button. Another way to customise may even require that the user find the hot link, a feature which could be used in applications such as games.

With various options and the ability to use the authoring tool to customise, HotVideo may be used for virtually any application that contains a video. It can be easily adapted to other programs, which opens up endless possibilities. It is considered a platform for interactive videos. Naturally, it could enhance the depth and effectiveness of Web pages as well as presentation videos, DVD`s or digital videos. TV networks could use HotVideo to explore new forms of programming, giving them the ability to learn about customer preferences or sell subsidiary services. For example, a travel program might sell HotVideo links to the sites of travel agencies, airlines, shops or other businesses that were featured in that program. HotVideo may have its roots in the Internet, but its possible uses go far beyond the world wide web.

Scene Based Graphics Rendering

  

In the pursuit of photo realism in conventional polygon based computer graphics, models have become so complex that most of the polygons are smaller than one pixel in the final image. At the same time, graphics hardware systems at the very high end are becoming capable of rendering, at interactive rates, nearly as many triangles per frame as there are pixels on the screen. Formerly, when models were simple and the triangle primitives were large, the ability to specify large, connected regions with only three points was a considerable efficiency in storage and computation. Now that models contain nearly as many primitives as pixels in the final image, we should rethink the use of geometric primitives to describe complex environments.

An alternative approach is being investigated that represents complex 3D environments with sets of images. These images include information describing the depth of each pixel along with the colour and other properties. Algorithms have been developed for processing these depth enhanced images to produce new images from viewpoints that were not included in the original image set. Thus, using a finite set of source images, it is now possible to produce new images from arbitrary viewpoints.

The potential impact of using images to represent complex 3D environments includes:

Naturally photo-realistic rendering, because the source data are photos. This will allow immersive 3D environments to be constructed for real places, enabling a new class of applications in entertainment, virtual tourism, telemedicine, telecollaboration, and teleoperation.

Computation proportional to the number of output pixels rather than to the number of geometric primitives as in conventional graphics. This should allow

implementation of systems that produce high quality, 3D imagery with much less hardware than used in the current high performance graphics systems.

A hybrid with a conventional graphics system. A process called post rendering warping allows the rendering rate and latency to be decoupled from the user's changing viewpoint. Just as the frame buffer decoupled screen refresh from image update, post-rendering warping decouples image update from viewpoint update. This approach will enable immersive 3D systems to be implemented over long distance networks and broadcast media , using inexpensive image warpers to interface to the network and to increase interactivity.

Design of current graphics hardware has been driven entirely by the processing demands of conventional triangle based graphics. It is possible that very simple hardware may allow for real-time rendering using this new paradigm. It should be possible to write software only implementations that produce photo realistic renderings at much higher rates than with conventional graphics primitives.

DataHiding  

A major concern for creators of digital content, whether it's Web content, music, or movies on digital disc, is to protect their work from unauthorised copying and distribution. IBM researchers have developed a technology called DataHiding that enables the embedding of data (such as digital IDs or captions) invisibly.

Hiding Information

 

DataHiding is a technology that allows owners of content to embed data invisibly or inaudibly into other digital media, such as video, audio data, or still images. When the data is embedded, it is not written as part of the data header, but rather embedded directly into the digital media itself. This process changes the original digital data, but the change is so slight that it cannot be visually detected, and has no impact on the performance of the original data.

The beauty of DataHiding is that it gives content creators a powerful means of marking their digital creations without affecting the end user's appreciation of it. The embedded information does not change the size of the original data, and it survives normal image processes such as compression and format transformation.

Who Can Use It

 

DataHiding can be a useful tool for anyone associated with creating or distributing digital content. In addition to authors, it could be used by copyright agencies to detect unauthorised copies of digital content, by authorised reproduction studios to ensure that that have valid copies of digital content, or even for comments that can be inserted in various revisions of digital content.

One of the biggest markets of DataHiding may be in the emerging DVD market. Content providers have been concerned about the ability of casual users to make a clear copy illegally. DataHiding technology could enable content creators and distributors to build systems that could effectively prevent illegal copying.

Fractal Image Compression

  

Data compression is nothing new, it's used by most modems. If you download information from the Internet, you probably will be using some sort of utility, such as Winzip or StuffIt, to decompress the information. These utilities preserve all of the information in the original file, performing what's technically called lossless compression which is obviously important if you're compressing a program file or formatted text document.

Compression of graphic images, on the other hand, does not preserve all of a file's data. Lossy compression sacrifices precision in order to make the resulting file more compact. The assumption is that most people don't notice the loss of small details, especially if they're watching a video or looking at a newspaper style photograph.

The standard method of lossy compression employs the JPEG technology, named for the Joint Photographic Experts Group, which first approved the standard. JPEG breaks down an image into a grid and uses a fairly simple mathematical formula to simplify the visual information contained in each square of the grid. This reduces the space needed to store the image, but degrades the quality of the image, often making it look blocky. A higher compression ratio equals greater image distortion.

Fractal compression could change the assumptions behind lossy and lossless compression. Invented in the 1980s by Michael Barnsley and Alan Sloan, two mathematicians at Georgia Tech, fractal compression is based on the discovery by Benoit Mandelbrot, an IBM scientist, that a hidden geometry exists in apparently random patterns of nature. Further studies of fractals

revealed that images, from mountains to clouds to snowflakes can be built from simple fractal patterns.

In fractal theory, the formula needed to create part of the structure can be used to build the entire structure. For example, the formula to create the pattern for a tiny piece of a fern can be used to create the entire fern leaf. Barnsley's discovery was that the process could be used in reverse. Barnsley patented a technology that takes real world images, analyses them, and breaks them down into groups of fractals, which can be stored as a series of fractal instructions. These instructions take up much less space than the bit-mapped images used in jpeg technology.

It took Barnsley's company, Iterated Systems, almost six years to perfect the technique of fractal compression to the point where it was commercially viable. The company's claims that it can achieve compression ratios of 20,000 to 1.

Fractal compression technology from Iterated Systems does indeed provide higher compression ratios and better image quality than anything else on the market. Photographic images can be compressed from 20:1 and 50:1 with no noticeable loss in resolution, and the company also claims that it can compress images with a ratio of more than 200:1 and maintain acceptable resolution. This is unmatched by jpeg or any other current technology and holds a tremendous amount of promise for delivering a wide range of graphics and multimedia technologies, from colour fax transmission to full motion video over telephone lines.

Because fractal images are stored as mathematical formulas rather than as bit maps, they can be decompressed to resolutions that are higher or lower than those of the original. The ability to scale images without distortion is one of fractal compression's important advantages over jpeg. Fractal compression can also improve as you apply more processing power, you can improve both the amount of compression as well as the quality of the image by just letting the system process the image longer. This upfront processing requirement is fractal compression's biggest drawback. On a typical microcomputer, it would take about 900 hours to compress a single hour of video. This underscores the fact that fractal compression is an asymmetric system, it takes ages to compress, but decompressing is quick. jpeg, on the other hand, is a symmetric compression system, it takes the same amount of time to compress and decompress a file. This makes jpeg more suitable for some applications, but makes fractal compression ideal for applications like video on demand.

Iterated also has stumbled on another revolutionary aspect of the technology called fractal image enhancement a process that can actually add details missing from the uncompressed scanned image or digital file. The process works by calculating what information was probably left out of the image when it was originally broken down into a grid of pixels. This technique could also allow images to be greatly enlarged without showing pixel chunks or otherwise losing detail, think wall sized HDTV.

Microsoft was so impressed with Iterated Systems's advances, it licensed the company's fractal compression technology for use in its Encarta CD-ROM, a multimedia encyclopedia that contains more than 10,000 colour images. And the us Commerce Department recently granted the company $2 million to develop a low cost fractal decompression chip that can keep pace with the frame rate of television.

It may be possible to improve fractal compression technology even further by refining the formulas that recognize fractal patterns. There's a problem, though, Iterated Systems has obtained a patent on its compression technology, but is currently unwilling to reveal the exact nature of the algorithms (which are trade secrets) used in the process. This means that the technology will only advance at whatever rate a single company - Iterated - decides to set

Future Compression Technologies

  

Over the last couple of years there has been a great increase in the use of video in digital form due to the popularity of the Internet. We can see video segments in Web pages, we have DVD`s to store video and HDTV will use a video format for broadcast. To understand the video formats, we need to understand the characteristics of the video and how they are used in defining the format.

Video is a sequence of images which are displayed in order. Each of these images is called a frame. We cannot notice small changes in the frames like a slight difference of colour so video compression standards do not encode all the details in the video, some of the details are lost. This is called lossy compression. It is possible to get very high compression ratios when lossy compression is used. Typically 24 to 30 frames are displayed on the screen every second. There will be lots of information repeated in the consecutive frames. If a tree is displayed for one second then 30 frames contain that tree. This information can be used in the compression and the frames can be defined based on previous frames. So consecutive frames can have information like "move this part of the tree to this place". Frames can be compressed using only the information in that frame (intraframe) or using information in other frames as well (interframe). Intraframe coding allows random access operations like fast forward and provides fault tolerance. If a part of a frame is lost, the next intraframe and the frames after that can be displayed because they only depend on the intraframe.

Every colour can be represented as a combination of red, green and blue. Images can also be represented using this colour space. However this colour space called RGB is not suitable for compression since it does not consider

the perception of humans. YUV colour space where only Y gives the greyscale image. Human eye is more sensitive to changes is Y and this is used in compression. YUV is also used by the NTSC, PAL, SECAM composite colour TV standards.

Compression ratio is the ratio of the size of the original video to the size of the compressed video. To get better compression ratios, pixels are predicted based on other pixels. In spatial prediction, a pixel can be obtained from pixels of the same image, in temporal prediction, the prediction of a pixel is obtained from a previously transmitted image. Hybrid coding consist if a prediction in the temporal dimension with a suitable decorrelation technique in the spatial domain. Motion compensation establishes a correspondence between elements of nearby images in the video sequence. The main application of motion compensation is providing a useful prediction for a given image from a reference image.

DCT (Discrete Cosine Transform) is used in almost all of the standardised video coding algorithms. DCT is typically done on each 8x8 block. 1-D DCT requires 64 multiplications and for an 8x8 block 8 1-D DCTs are needed. 2-D DCT requires 54 multiplications and 468 additions and shifts. 2-D DCT is used in MPEG, there is also hardware available to do DCT. When DCT is performed, the top left corner has the highest coefficients and bottom right has the lowest, this makes compression easier. The coefficients are numbered in a zig zag order from the top left to bottom right so that there will be many small coefficients at the end. The DCT coefficients are then divided by the integer quantisation value to reduce precision. After this division it is possible to loose the lower coefficients if they are much smaller than the quantisation. The coefficients are multiplied by the quantisation value before IDCT (inverse DCT).

 

MPEG-2

MPEG-2 is designed for diverse applications which require a bit rate of up to 100Mbps. Digital high-definition TV (HDTV), DVD, interactive storage media (ISM), cable TV (CATV) are sample applications. Multiple video formats can be used in MPEG-2 coding to support these diverse applications. MPEG-2 has bitstream scalability: it is possible to extract a lower bitstream to get lower resolution or frame rate. Decoding MPEG-2 is a costly process, bitstream scalability allows flexibility in the required processing power for decoding. MPEG-2 is upward, downward, forward and backward compatible. Upward compatibility means the decoder can decode the pictures generated by a lower resolution encoder. Downward compatibility implies that a decoder can decode the pictures generated by a higher resolution encoder. In a forward compatible system, a new generation decoder can decode the pictures generated by an existing encoder and in a backward compatible system, existing decoders can decode the pictures generated by new encoders.

In MPEG-2 the input data is interlaced since it is more oriented towards television applications. Video sequence layers are similar to MPEG-1 the only improvements are field/frame motion compensation and DCT processing, scalability. Macroblocks in MPEG-2 has 2 additional chrominance blocks when 4:2:2 input format is used. 8x8 block size is retained in MPEG-2, in scaled format blocks can be 1x1, 2x2, 4x4 for resolution enhancement. P and B frames have frame and field motion vectors.

MPEG-4

Success of digital television, interactive graphics applications and interactive multimedia encouraged MPEG group to design MPEG-4 which allows the user to interact with the objects in the scene within the limits set by the author. It also brings multimedia to low bitrate networks.

MPEG-4 uses media objects to represent aural, visual or audiovisual content. Media objects can be synthetic like in interactive graphics applications or natural like in digital television. These media objects can be combined to form compound media objects. MPEG-4 multiplexes and synchronises the media objects before transmission to provide quality of service and it allows interaction with the constructed scene at receiver`s machine.

MPEG-4 organises the media objects in a hierarchical fashion where the lowest level has primitive media objects like still images, video objects, audio objects. MPEG-4 has a number of primitive media objects which can be used to represent 2 or 3-dimensional media objects. MPEG-4 also defines a coded representation of objects for text, graphics, synthetic sound, talking synthetic heads.

MPEG-4 provides a standardised way to describe a scene. Media objects can be places anywhere in the coordinate system. Transformations can be used to change the geometrical or acoustical appearance of a media object. Primitive media objects can be grouped to form compound media objects. Streamed data can be applied to media objects to modify their attributes and the user`s viewing and listening points can be changed to anywhere in the scene.

The visual part of the MPEG-4 standard describes methods for compression of images and video, compression of textures for texture mapping of 2-D and 3-D meshes, compression of implicit 2-D meshes, compression of time-varying geometry streams that animate meshes. It also provides algorithms for random access to all types of visual objects as well as algorithms for spatial, temporal and quality scalability, content-based scalability of textures, images and video. Algorithms for error robustness and resilience in error prone environments are also part of the standard.

For synthetic objects MPEG-4 has parametric descriptions of human face and body, parametric descriptions for animation streams of the face and body. MPEG-4 also describes static and dynamic mesh coding with texture mapping, texture coding with view dependent applications.

MPEG-4 supports coding of video objects with spatial and temporal scalability. Scalability allows decoding a part of a stream and construct images with reduced decoder complexity (reduced quality), reduced spatial resolution, reduced temporal resolution., or with equal temporal and spatial resolution but reduced quality. Scalability is desired when video is sent over heterogeneous networks, or the receiver can not display the video at full resolution.

Robustness in error prone environments is an important issue for mobile communications. MPEG-4 has 3 groups of tools for this. Resynchronisation tools enables the resynchronisation of the bitstream and the decoder when an error has been detected. After synchronisation data recovery tools are used to recover the lost data. These tools are techniques that encode the data in an error resilient way. Error concealment tools are used to conceal the lost data. Efficient resynchronisation is key to good data recovery and error concealment.

Fractal-Based coding

Fractal coding is a new and promising technique. In an image values of pixels that are close are correlated. Transform coding takes advantage of this observation. Fractal compression takes advantage of the observation that some image features like straight edges and constant regions are invariant when rescaled. Representing straight edges and constant regions efficiently using fractal coding is important because transform coders cannot take advantage of these types of spatial structures. Fractal coding tries to reconstruct the image by representing the regions as geometrically transformed versions of other regions in the same image.

See Fractal Compression

 

Model-based Video Coding

Model based schemes define three dimensional space structural models of the scene. Coder and decoder use an object model. The same model is used by coder to analyse the image, and by decoder to generate the image. Traditionally research in model based video coding focuses on head modeling, head tracking, local motion tracking, and expression analysis, synthesis. Model based video coding have bean mainly used for video conferencing and video telephony since mostly the human head is modeled. Model based video coding has concentrated in modeling of images like the head and shoulders because it is impossible to model every object that may be in the scene. There is lots of interest in applications such as speech driven image animation of talking heads and virtual space teleconferencing.

In model-based approaches a parametrised model is used for each object in the scene. Coding and transmission is done using the parameters associated with the objects. Tools from image analysis and computer vision is used to analyse the images and find the parameters. This analysis provides information on several parameters like size, location, and motion of the objects in the scene. Results have shown that it is possible to get good visual quality at rates as low as 16kbps.

Scalable Video Coding

 

Multimedia communication systems may have nodes with limited computation power to be used for decoding and heterogeneous networks such as combination of wired and wireless networks. In these cases we need the ability to decode at a variety of bit rates. Scalable coders have this property. Layered multicast has been proposed as a way to provide scalability in video communication systems.

MPEG-2 has basic mechanisms to achieve scalability but it is limited. Spatiotemporal resolution pyramids is a promising approach to provide scaleable video coding. Open loop and closed loop pyramid coders both provide efficient video coding and inclusion of multiscale motion compensation. Simple filters can be used for spatial downsampling and interpolation operations and fast and efficient codecs can be implemented. Morphological filters can also be used to improve image quality.

Pyramid coders have multistage quantisation scheme. Bit allocation to the various quantisers depending on the image is important to get efficient compression. Optimal bit allocation is optimally computationally infeasible when pyramids with more than two layers are used. Closed loop pyramid coders are better suited for practical applications then open loop pyramid coders since they are less sensitive to suboptimal bit allocations and simple heuristics can be used.

There are several ways to utilise multistage motion compensation. Efficiently computing motion vectors and then encoding them by hierarchical group estimation is one way. When video is sent over heterogeneous networks scalability is utilised by offering a way to reduce the bit rate of video data in case of congestion. By using priorities the network layer can reduce bitrate without knowing the content of the packet or informing the sender.

 

Wavelet-based Coding

Wavelet transform techniques have been investigated for low bit rate coding. Wavelet based coding has better performance than traditional DCT based coding. Much lower bit rate and reasonable performance are reported based on the application of these techniques to still images. A combination of

wavelet transform and vector quantisation gives better performance. Wavelet transform decomposes the image into a multi frequency channel representation, each component of which has its own frequency characteristics and spatial orientation features that can be efficiently used for coding. Wavelet based coding has two main advantages: it is highly scaleable and a fully embedded bitstream can be easily generated. The main advantage over standard techniques such as MPEG is that video construction is achieved in a fully embedded fashion. Encoding and decoding process can stop at a predetermined bit rate. The encoded stream can be scaled to produce the desired spatial resolution and frame rate as well as the required bit rate. Vector quantisation makes use of the correlation and the redundancy between nearby pixels or between frequency bands. Wavelet transform with vector quantisation exploits the residual correlation among different layers if the wavelet transform domain using block rearrangement to improve the coding efficiency. Further improvements can also be made by developing the adaptive threshold techniques for classification based on the contrast sensitivity characteristics of the human visual system. Joint coding of the wavelet transform with trellis coded quantisation as a joint source channel coding is an area to be considered.

Additional video coding research applying the wavelet tranform on a very low bit rate commmunication channel is performed. The efficiency of motion compensated prediction can be improved by overlapped motion compensation in which the candidate regions from the previous frame are windowed to obtain a pixel value in the predicted frame. Since the wavelet transform generates multiple frequency bands, multifrequency motion estimation is available for the transformed frame. It also provides a representation of the global motion structure. Also, the motion vectors in lower frequency bands are predicted with the more specific details of higher frequency bands. This hierarchical motion estimation can also be implemented with the segmentation technique that utilises edge boundaries from the zero crossing points in the wavelet transform domain. Each frequency band can be classified as temporal activity macroblocks or no temporal activity macroblocks. The lowest band may be coded using DCT, and the other bands may be coded using vector quantisation or trellis coded quantisation.

The Next Generation Internet

 

By now, anyone who reads the morning paper has probably heard that the Internet will be an even bigger deal in the future than it is today. School children will access all the great works of literature ever written with the click of a mouse, surgery will be performed via cyberspace, all transactions with the government will be conducted via your personal computer, making bureaucratic line ups a thing of the past.

Sound too good to be true? Much of what has been written about two buzzword initiatives, Internet2 (I2) and the Next Generation Internet (NGI), would lead one to believe that these scenarios are just around the corner.

And some may be. Already in the works are projects to split the spectrum of light traveling the Internet's optical networks, allowing high priority traffic to pass at the highest and least interrupted frequency, while passing low priority traffic (i.e. your e-mail) along at a lower frequency. Teleinstrumentation the remote operation of such rare resources as satellites and electron microscopes has been demonstrated. Digital libraries containing environmental data have been used to simulate natural and man made disasters for emergency response teams. Classrooms and entire universities have gone online, making remote education an option for students.

But misconceptions about I2 and NGI abound, first and foremost that they are interchangeable terms for the same project, closely followed by the perception that the government is hard at work right now digging trenches and laying cable for what is to be a brand new Internet.

I2 and NGI are separate and distinctly different initiatives. It's easiest to think of them as two different answers to the same plaguing problem. The problem is congestion on the commercially available Internet.

 

The need for a new Internet

 Prior to 1995, the National Science Foundation's (NSF) NSFnet served the research and academic community and allowed for cross country communications on relatively unclogged T3 (45 megabit per second) lines that were unavailable for commercial use. However, NSFnet went public in 1995, setting the stage for today's Internet. As the Internet has become irrevocably a part of life, the increase in e-mail traffic and the proliferation of graphically dense pages have eaten up valuable bandwidth.

With all of this data congealing in cyberspace, for the Internet currently knows no differentiation between a Web site belonging to Arthur Andersen or Pamela Anderson there has arisen a critical need for a new Internet. The answers to the questions for what purpose and for who's use vary depending upon the proposed solution.

 

Internet2: The bottom-up initiative

 

Internet2 is the university community's response to the need for a return to dedicated bandwidth for academic and research use exclusively. Currently, about 120 universities and 25 corporate sponsors are members of Internet2,

which in October 1997 incorporated itself forming the University Corporation for Advanced Internet Development (UCAID).

UCAID now serves as the support and administrative organisation for the project known as Internet2. Members pay an annual fee of between $10,000 and $25,000 and must demonstrate that they are making a definitive, substantial, and continuing commitment to the development, evolution, and use of networking facilities and applications in the conduct of research and education before they are approved for membership.

Internet2 represents the interests of the academic community through its concentration on applications that require more bandwidth and end to end quality of service than is available relying upon the commercial Internet. I2 is focused upon the needs of academia first, but is expected to develop technologies and applications that will eventually make their way into the rest of society.

 

The vBNS: A prototype for both Internets

 

The vBNS (very-high-performance Backbone Network Service), a project of the National Science Foundation and MCI Telecommunications, is a nationwide network that supports high performance, high bandwidth research applications. Like the old NSFnet, vBNS is a closed network, available only to the academic and research community. Currently it connects 46 academic institutions across the country, though a total of 92 have been approved for connectivity. A component of the vBNS project is research into high speed networking and communications and transfer of this data to the broader networking community. In many ways, the vBNS is the prototype for both I2 and NGI. The kinds of applications that both I2 and NGI would like to foster are currently deployed on this network.

Since its formation in 1996, I2 has concentrated on defining the environment where I2-type applications will run, holding member meetings and demonstrations where developers express programming needs and innovations that will be incorporated into a set of network tools that do not currently exist. One such meeting is scheduled to be held later this month at the Highway 1 technology forum in Washington, D.C.

I2 member meetings also provide a forum for researchers to investigate trends that will contribute to the applications environment, including object oriented programming, software componentisation, object request brokering, dynamic run time binding, multitiered applications delivery with separation of data, and presentation functions.

Internet2 also continues to define its relationship with the other Internet initiative, Next Generation Internet, at the same time as NGI explores how best to apply the experience and expertise of the I2 community to its task. While

acknowledging their differences, in statements each initiative positions its relationship to the other, determining where the line between the two could or should be drawn and what benefit each brings to the other's agenda.

The NGI roadmap

The NGI initiative is divided into three progressive stages, called goals in NGI parlance. Goal 1 is underway now, Goal 3 is targeted for the end of next year.

Goal 1 calls for NGI to research, develop, and experiment with advanced network technologies that will provide dependability, diversity in classes of service, security, and realtime capability for such applications as wide area distributed computing, teleoperation, and remote control of experimental facilities. In this first phase, the project, led by the Defense Advanced Research Projects Agency (DARPA) - will set the stage for the technologies, applications, and test beds envisioned for Goals 2 and 3.

Goal 2 led by the NSF constructs the actual NGI networks and also depends heavily upon the vBNS. NGI expects that Goal 1 development will, by this point, have overcome the speed bumps of incompatible performance capabilities and service models in switches, routers, local area networks, and workstations. In Goal 2, 100 sites (universities, federal research institutions, and other research partners) will be connected at speeds in excess of 100 times that of today's Internet.

As with I2, the vBNS would serve as a backbone for the network connecting NGI participants. To bring in other research partners and provide additional connectivity, the vBNS would interconnect to other federal research networks, including DREN (Defense), NREN (NASA), ESnet (DoE), and eventually SuperNet (DARPA's terabyte research network). The vBNS would also serve as a base for interconnecting to foreign high-performance networks, including the Canadian CA*net II, and others routed through the Science, Technology, and Research Transit Access Point (STAR-TAP) in Chicago.

Goal 2 of the NGI project also has the most planned collaboration with Internet2. NGI officials foresee the NSF supporting the GigaPoPs that would interconnect the I2 institutions and coordinating I2 and NGI interconnectivity to support interoperability and shared experimentation with NGI technologies and applications.

 

The Internet speed comes in the second, high-risk, high-security, test bed planned for the second phase of Goal 2. In this phase, 10 sites will be connected on a network employing ultra high speed switching and transmission technologies and end to end network connectivity at more than 1 gigabit per second, approximately 1000 times faster than today's Internet. This 1 gigabit per second network is intended to provide the research base for an eventual Terabyte per second network that would employ NGI conceived and developed technologies for harnessing such speed. A 1 Terabyte per second

network additionally takes advantage of optical technology pioneered by DARPA. 

The impossible becomes commonplace

The current Internet exploded once it was opened up for commercial use and privatisation. Both I2 and NGI include industry as part of their advisory and actual or envisioned working teams, a nod to the future when the technologies or applications developed within either initiative, be they Terabyte per second networks, quality of service tools, digital libraries, or remote collaboration environments, are ready for and applicable to the market place.

On today's Internet it sometimes takes many seconds to get one picture, while on tomorrow's Internet, you're going to get many pictures in one second. This means high definition video, such as that being used now for scientific visualisation. It's only a matter of time until industry seizes upon and spins this technology off into other worlds of interest to folks outside the sciences, like the entertainment industry.

Both initiatives have obstacles before them, I2 depends upon academic resources and investment, and NGI relies on Congressional budgets and endorsement.

Still, there is cautious hope within their respective communities that I2 and NGI can create not a new Internet, but a new Internet environment.

Teledesic

The Orbiting

Internet  

Teledesic was formed in June of 1990 with the objective of creating a means of providing affordable access to advanced network connections to all those parts of the world that will never get such advanced capabilities though existing technologies.

Information is becoming increasingly essential to all those things we associate with quality of life: economic opportunity, education, health care, and public services. Yet, most people and places in the world do not now have access even to basic telephone service. Even those who do have access to basic phone service get it through 100 year old technology - analog copper wire networks, that for the overwhelming part will never be upgraded to an

advanced digital capability. Even in the developed countries, there is a risk that whole areas and populations will be denied access to the powerful digital technologies that are changing the world.

The digital revolution is just as fundamental as the industrial revolution and the agricultural revolution before that. It will change all aspects of our societies. Those previous changes took place over many generations, indeed in parts of the world they are still ongoing today. Driven by advances in microelectronics technologies, where product generations are measured in months, the digital revolution is taking place at a breathtaking pace. The digital technologies that grow more powerful every day in our notebook computers will soon be exploding out through network connections. Yet, outside of the most advanced urban areas, most of the world will never get access to these technologies through conventional wireline means.

While there is a lot of fiber out there in the world, and the number of places is growing, it is used primarily to connect countries and telephone company central offices. Even in Europe, little of that fiber will be extended for local access to individual offices and homes, which represents 80 percent of the cost of a network. In most of the world, fiber deployment likely never will happen.

This is a big problem for all of our societies. If these powerful technologies are available only in advanced urban areas, people will be forced to migrate to those areas in search of economic opportunity and to fulfill other needs and desires. Society now is organised around the economics of infrastructure. With the agricultural revolution, technology tied people to the land and brought them together in towns and villages. With the industrial revolution, people came together in increasingly congested urban areas, all organised around the economics of industrial infrastructure - wires, rails, highways, pipes, machinery. To the extent the digital revolution is tied to wires, it is just an extension of the industrial age paradigm. Like the highways and the railways before that, wires are rigidly dedicated to particular locations. If you live along side the main line you prosper. If you live a few miles distant, you are left behind.

To date, Teledesic has received most of its funding from Bill Gates, the founder of Microsoft, the world's largest computer software company and Craig McCaw who founded McCaw Cellular, the world's largest cellular communications service provider before its sale to AT&T in 1994. Their investment is symbolic, as well as financial.

Moore's Law, which says that a microprocessor will do twice as much for the same cost every 18 months, has correctly predicted the exponential growth of the computer industry for over 20 years. However, while computers today are thousands of times faster than those available a decade or two ago, networking has shown only linear growth. Improvements in networking performance, which have required the digging up of the streets and replacement of the antiquated copper with modern fiber optic technology, have not come close to keeping pace.

The solution is wireless access to advanced network connections. Unlike wireline technologies, the cost of wireless access is largely indifferent to location. But to get the bandwidth required for fiber like service through wireless means, it is necessary to move way up in to the millimeter wave frequencies in the 20 to 30 GHz range (the Ka band). But, sending signals horizontally, over the land, in those frequencies is problematic. They are subject to rain attenuation and blocking by terrain, foliage, and buildings. The solution adopted was simple. Send the signals vertically. This leads to a satellite based solution.

To ensure seamless compatibility with those fiber networks, it is important that the satellite network have the same essential characteristics as fiber. Those characteristics include: broadband channels, low error rates, and low delay.

The advanced digital broadband networks will be packet switched networks in which voice, video, and data are all just packets of digitised bits. In these networks you cannot separate out the applications that can tolerate delay from those that can't. People will not want to maintain two networks: one for delay sensitive applications and another for applications that can tolerate delay. Traditional geostationary orbit (GSO) satellites will never be able to provide fiber like quality of service.

This leads to a low Earth orbit (LEO) network. To put this in perspective, the space shuttle orbits at about 250 kilometers above Earth's surface. There is only one geostationary orbit, and that is over the equator at 36,000 kilometers almost 150 times further out than the space shuttle. By contrast, Teledesic's satellites would orbit at about 700 kilometers, 50 times closer to Earth than geostationary satellites.

With the combination of a very high minimum vertical angle to the satellite to overcome the blocking and attenuation problems associated with the Ka band and the low altitude, geometry takes over, and a constellation of hundreds of satellites is required to cover Earth. The large number of satellites also allows economies of scale in manufacturing and creates a system with very large capacity which allows a low cost of service.

The concept of a network consisting of hundreds of satellites may seem like a radical concept when compared to traditional geostationary satellites but it is less radical when compared with the evolution of networks on the ground. Computer networks have evolved from centralised systems built around a single mainframe computer to distributed networks of interconnected PCs. Similarly, satellite networks (for switched network connections) are evolving from centralised systems built around a single geostationary satellite to distributed networks of interconnected LEO satellites. The evolution in both cases is being driven by some of the same forces.

A decentralised network offers other advantages: A distributed topology provides greater reliability. Redundancy and reliability can be built more economically into the network rather than the individual unit. Also, because a LEO satellite has a smaller footprint within which frequencies can be reused, it is inherently more efficient in its use of spectrum resources. Geostationary satellites will continue to have an important role to play, particularly for broadcast applications where their large footprint is advantageous. But increasingly, geostationary satellites will coexist with non-geostationary orbit (NGSO) satellite networks.

This evolution toward NGSO systems has resulted in three LEO system types, each focused on a different service segment and using a different portion of the radio frequency spectrum. The best way of distinguishing between these three LEO system types is by reference to their corresponding terrestrial services:

The so-called little LEOs, like OrbComm, are the satellite equivalent of paging. They operate below 1 GHz, and provide simple store and forward messaging. These systems offer low data rates but can provide valuable services in a wide range of settings, such as remote monitoring and vehicle tracking.

The so-called big LEOs like Iridium, Globalstar and ICO, have received the most attention. They are the satellite equivalent of cellular phone service, and operate between 1 and 3 GHz.

Teledesic is the first proposed broadband LEO. It will provide the satellite equivalent to optical fiber. Because it will operate in the Ka band, essentially line of sight from the user terminal to the satellite is required, which makes it more appropriate for fixed applications, or mobile applications like maritime and aviation use, where line of sight is not an issue. It will provide the advanced, digital broadband network connections to all those parts of the world that are not likely to get those capabilities through wireline means.

When Teledesic was first publicised in early 1994, most people seemed to have difficulty comprehending the services that the Teledesic Network would provide. It is not cellular like hand-held phones, like Iridium and Globalstar, and it is not broadcast video delivery, like Hughes's DirecTV.

Since then, the emergence of the World Wide Web and network-centric computing have provided a compelling model for a different kind of telecommunications: switched, broadband services. Peer to peer networking,

based on the ubiquity and exponential improvements of personal computing, is transforming the way individuals live and businesses create value. Switched connections communicate from anyone to anyone, and broadband allows the transmission of all forms of digital information, voice, data, videoconferencing, and interactive multimedia.

The Internet today is still at a relatively primitive stage of development, comparable to the first personal computers in the late 1970s. At that time, it was difficult to imagine the pervasiveness and range of applications of personal computing today. By contrast, the World Wide Web already provides a revealing glimpse of the promise of the Internet, with tens of thousands of companies and millions of individuals exploring, publishing and developing on this new medium. Any and all information can and will be digitised, uploaded, and transmitted anywhere.

Well, not quite anywhere. The promise of the information age is constrained by the lack of access to switched, broadband services in most of the developed and virtually all of the developing world. The Teledesic Network will provide a means to help extend these switched, broadband connections on demand anywhere on Earth.

There is an important aspect of these non-geostationary satellite systems that is worth noting. There have been many studies, many of them by the ITU, that show a direct correlation between economic prosperity and teledensity. In the absence of a high level of economic development, however, a country is not likely to attract the investment required for an advanced information infrastructure. NGSO systems like Teledesic can help developing countries overcome this problem in telecommunications development.

Once you come out of a geostationary orbit, then by definition, satellites move in relation to Earth. With an NGSO system, continuous coverage of any point requires, in effect, global coverage. In order to provide service to the advanced markets, the same quality and quantity of capacity has to be provided to the developing markets, including those areas to which no one would provide that kind of capacity for its own sake. In this sense, NGSO satellite systems represent an inherently egalitarian technology that promises to radically transform the economics of telecommunications infrastructure. It is a form of cross-subsidy from the advanced markets to the developing world, but one that does not have to be enforced by regulation but rather is inherent in the technology.

Even at the speed of light, round trip communications through a geostationary satellite entail a minimum transmission latency end to end delay of approximately half a second. This latency causes the annoying delay in many intercontinental phone calls, impeding understanding and distorting the personal nuances of speech. What can be an inconvenience for analogue voice transmissions, however, can be untenable for videoconferencing and many data applications.

Excessive latency causes otherwise high bandwidth connections to communicate at a fraction of their capacity. And these issues arise not with

obscure data protocols or obsolete hardware, but with almost all implementations of the only data protocol with which most people are familiar, TCP/IP, which connects the global Internet and is the standard for corporate networking.

For all lossless protocols that guarantee the integrity of the data transmission, latency is a constraining factor on the usable bandwidth. Since a data packet may be lost in transmission, a copy of it must be kept in a buffer on the sending computer until receipt of an acknowledgment from the computer at the other end that the packet arrived successfully. Most common data protocols operate on this principle. The data packet's trip over the geostationary connection takes 250 milliseconds at best, and the acknowledgment packet takes another 250 milliseconds to get back, so the copy of the data packet cannot be removed from the buffer for at least 500 milliseconds. Since packets cannot be transmitted unless they are stored in the buffer, and the buffer can only hold a limited number of packets, no new packets can be transmitted until old ones are removed when their acknowledgments are received.

Specifically, the default buffer size in the reference implementation of TCP/IP is 4 kilobytes, which is 32 kilobits. This means that at any given moment, only 32 kilobits can be in transit and awaiting acknowledgment. No matter how many bits the channel theoretically can transmit, it still takes at least half a second for any 32 bits to be acknowledged. So, the maximum data throughput rate is 32 kilobits per half second, or 64 kilobits per second.

To put this in perspective, if you take off the shelf hardware and software, hook up a broadband geostationary link, and order a T1 line (1.544 megabits per second), you expect to be able to transmit about a T1 line worth of data. In fact, any connection via a geostationary satellite is constrained to only 64 kilobits per second, which is 4 percent of the purchased capacity.

Changing protocols is not a feasible solution to this situation. The trend in data networking is toward a single pipe carrying many types of data (including voice and other real-time data). It is therefore likely to be neither useful nor economical to transmit specific kinds of data using custom, proprietary protocols. In theory, the implementations of standard protocols, such as TCP/IP, can be modified to support higher buffer sizes. But these modifications are rarely simple or convenient, as computers on both sides of any connection need to be upgraded. Moreover, the maximum buffer size possible in TCP/IP is 64 kilobytes, which still only provides 1.024 megabits per second, or 67 percent of a T1 line over a geostationary link.

Even worse, if the geostationary link is not at one of the endpoints of the data transmission but is instead an intermediate connection, there is no method to notify the transmitting computer to use a larger buffer size. Thus, while data packets can seamlessly traverse multiple fiber and fiber like networks (such as Teledesic), geostationary links are unsuitable for seamless intermediate connections.

The interplay of latency and buffer sizes does not affect all data transmissions, only lossless ones. For real time data, such as voice and video, where it is not essential that all data be transmitted, lossy protocols can transmit higher data rates with less overhead. Unfortunately, real time applications, such as voice telephony and videoconferencing, are precisely the applications most susceptible to unacceptable quality degradation as a result of high latency.

Instead of attempting to modify the entire installed base of network equipment with which one might want to communicate, receiving seamless compatibility with existing terrestrial networks becomes increasingly attractive. As both bandwidth requirements and the use of real time data accelerate, the benefits of the fiber like service that Teledesic offers are only growing in importance.

What all of this discussion makes clear is that no one single technology or satellite system type is going to be appropriate for all communications needs in all settings. The capabilities of fiber cannot be matched for very dense traffic. For basic telephone service, the economics of terrestrial cellular systems are compelling, particularly where no wireline infrastructure exists. Geostationary satellites will continue to play an important role, particularly for video distribution and other broadcast applications, where latency is not an issue and a large footprint is desirable. And each of the LEO system types has an important role to play.

For the past 30 years of satellite communications, geostationary satellites have been virtually the entire relevant universe and the international satellite spectrum allocations and associated regulations reflect that. Geostationary satellites currently enjoy general priority status in all fixed satellite service frequency bands. This subjects NGSO satellite systems to unbounded regulatory uncertainty, as their operation would be vulnerable to preemption by any and all geostationary satellites, even those deployed long after the NGSO systems. For someone like Teledesic who proposes a non geostationary satellite system, special accommodation is required, by contrast, someone proposing a geostationary satellite system need only file the appropriate paperwork with the ITU.

In bands such as the C and Ku bands that already are congested with geostationary satellite systems, it would not be appropriate to change this regime. To allow for the future development of both satellite system types, however, designated sub bands in which non geostationary systems would have priority status need to be established in the satellite service expansion bands.

Of course, the value of systems like Teledesic or any technology ultimately is measured by their ability to enhance the quality and meaning of our lives. The benefits to be derived from the advanced information services they enable are as vast as the areas of need to which they can extend.

The Interplanetary Internet

  

Given that three quarters of the earth’s population does not have a telephone, let alone access to the World Wide Web, talk of extending the Internet to the moon, Mars and possibly an asteroid or two might sound rather premature. But plans for an interplanetary Internet (IPN) are already being drawn up. According to the scheme’s proponents, extending the network into space will reduce the cost of future space missions by making it easy for several Mars landers to share a single relay satellite to send data back to earth. At the same time, it could also benefit terrestrial users by encouraging research into ways of making wireless connections more reliable.

The problem is that outer space is likely to be as hostile to the networking protocols that underpin the Internet as it is to air breathing humanoids. For a start TCP/IP, the common language spoken by every device on the network, is a very chatty protocol. A constant buzz of greetings, acknowledgments and farewells travel between computers as they locate each other, exchange information and then disconnect. In space however such chattiness is a bad way of conversing. Radio signals take a second to reach the moon, and several minutes to reach Mars. So a new, terser protocol will be needed, to save both time and energy.

Another difficulty is that TCP/IP was designed to work over networks in which transmission errors are rare, but congestion is common. On earth when one device sends a packet of data to another and fails to receive an acknowledgment, it assumes that the link has become congested. It therefore reduces the rate at which it sends subsequent packets, only ramping that rate up again when the congestion has eased. In space, however, different rules apply. If a packet of data sent to a distant spacecraft in a hostile environment fails to get through, the cause is more likely to be a transmission error, in which case the correct response is to retransmit the packet as quickly as possible, rather than assuming that the link is congested and backing off.

File transfer is another area where new approaches will be required. At the moment sending a file (an image, for example) from one computer to another using the Internet’s File Transfer Protocol (FTP) involves establishing a connection between the source and destination machines, and then passing the file across in chunks. But if a rover on the Martian surface wants to send a file back to earth, this is an inefficient way of doing it. It would make more sense for the rover to hand the whole file over to a lander, which could pass it in chunks to orbiting relay satellites for transmission home.

Consideration of such matters sounds whimsical. But similar problems arise, in less drastic form, with wireless Internet devices on earth. Handheld

computers and wireless netphones would also benefit from a less chatty protocol, more efficient use of their limited battery power, the ability to cope in noisy environments, and an easier way to send files while on the move.

So rather than reinventing the wheel, the scientists working on IPN a consortium that includes researchers from America’s space agency, NASA, the Defence Advanced Research Projects Agency, the British National Space Centre and Britain’s Defence Evaluation and Research Agency, hope to collaborate with researchers in the terrestrial telecoms industry to establish new standards. The IPN working group has already drawn up a list of problems that need to be solved.

So far, the plans include the development of File Delivery Protocol (FDP), a modified form of FTP, and a new idea based around bundles of data in which multiple packets, requests, files and messages can be sent in one go.

The idea, eventually, is that separate Internets should exist on Earth, the moon, Mars and so on, connected by gateways that communicate over an interplanetary backbone using new spacefaring protocols. Probes landing on asteroids and comets would also connect to the IPN. The fact that different bodies in the solar system change their relative positions as they orbit the sun will complicate routing.

There is also the question of names and addresses. The IPN plans call for an extension to the domain naming system to cover different planets and solar systems.

For example, websites on Earth would become www.website.com.earth.sol

But establishing these new domains even for experimental purposes could prove rather difficult.

The Next Generation Of Wireless Telephony

 

Europe has witnessed in recent years a massive growth in mobile communications, ranging from the more traditional analogue based systems to the current generation of digital systems such as GSM (Global System for Mobile Communications), DCS-1800 (Digital Communication System at 1800 MHz), ERMES (European Radio Messaging System), and to a lesser extent DECT (Digital European Cordless Telephone), and TETRA (Trans European Truncked Radio). The GSM family of products (GSM + DCS-1800), which represents the first large scale deployment of commercial digital cellular system ever, enjoys world wide success, having already been adopted by over 190 operators in more than 80 countries. In a very short period of time, the

percentage of European cellular subscribers using GSM or DCS-1800 has already exceeded 50%. In addition, the figure portrays the penetration rates of the combined analogue and digital cellular systems for the same time frame. It is worth noticing that the biggest markets of Europe in terms of subscribers (i.e., UK, Italy and Germany) are not the markets with the largest penetration rates. In this respect, the largest penetration rates are found in the Nordic countries, close to or even exceeding 25% of the population.

Third Generation systems and technologies are being actively researched world wide. In Europe, such systems are commonly referred under the name UMTS (Universal Mobile Telecommunications Systems) while internationally, and particularly in the ITU context, they are referred to as FPLMTS (Future Public Land Mobile Telecommunications Systems) or more recently IMT-2000 (International Mobile Telecommunications for the year 2000).

In this context, but also in a world wide perspective, with many competing mobile and personal communication technologies and standards being proposed to fulfill the users needs, the essential questions, to which no immediate, conclusive, firm answers can be given, are: To what extent, and how fast, will the users' requirements evolve beyond the need for voice and low data rate communications?, and which will be the technologies that will meet the requirements for mobile and personal communications services and applications beyond the year 2000?.

The rapid advance of component technology; the pressure to integrate fixed and mobile networks; the developments in the domains of service engineering, network management and intelligent networks; the desire to have multi-application hand-held terminals; and above all the increasing scope and sophistication of the multimedia services expected by the customer; all demand performance advances beyond the capability of second generation technology. The very success of second generation systems in becoming more cost effective and increasingly cost attractive raises the prospect that it will reach an early capacity and service saturation in Europe's major conurbations. These pressures will lead to the emergence of third generation systems representing a major opportunity for expansion of the global mobile marketplace rather than a threat to current systems and products.

The ground work for UMTS started in 1990, and some early answers can already be provided regarding its requirements, characteristics and capabilities, with the initial standards development process already under way at ETSI (European Telecommunications Standards Institute). The basic premise upon which work is being carried out, is that by the turn of the century, the requirements of the mobile users will have evolved and be commensurate with those services and applications that will be available over conventional fixed or wireline networks. The citizen in the third millennium will wish to avail himself of the full range of broadband multimedia services provided by the global information highway, whether wired or wireless connected.

Various international forums have raised the issue of technology migration from Second to Third Generation via the use of spectrum in the FPLMTS/UMTS

bands. This may result in the spectrum being allocated, in some parts of the world, in an inefficient piecemeal fashion to evolved Second Generation technologies and potentially many new narrow-application systems, thereby impeding the development of broadband mobile multimedia services.

Terminal, system and network technology as researched within the EU-funded ACTS projects, may alleviate to a large extent the complexity of the sharing of the spectrum between the Second and Third Generation systems. Finding the solution to the problem of evolution and migration path from Second (GSM, DCS-1800, DECT) to Third Generation systems (FPLMTS/UMTS), particularly from a service provision point of view, is also the subject of intense research carried out in the context of ACTS projects. Some of the key questions that are addressed include a detail consideration of the feasibility, as well as the cost effectiveness and attractiveness of the candidate enhancements. In this context, the ACTS projects will develop a set of guidelines aiming at reducing the uncertainties and associated investment risks regarding the new wireless technologies, by providing the sector actors and the investment community with clear perspectives on the technological evolution and on the path to the timely availability to the user of advanced services and applications.

In response to the imperatives of the internal European market, specific measures were taken, as early as 1987, to promote the Union-wide introduction of GSM, DECT, and ERMES. European Council Directives were adopted to set out common frequency bands to be allocated in each Member State to ensure pan-European operation, together with European Council Recommendations promoting the co-ordinated introduction of services based on these systems.

In 1994, the European Commission adopted a Green Paper on Mobile and Personal Communications with the aim of establishing the framework of the future policy in the field of mobile and personal communications. The Green Paper proposed to adapt, where necessary, the telecommunications policy of the European Union to foster a European-wide framework for the provision of mobile infrastructure, and to facilitate the emergence of trans-European mobile networks, services, and markets for mobile terminals and equipment.

Based on the Green Paper, the European Commission set out general positions on the future development of the mobile and personal sector, and defined an action plan which included actions to pursue the full application of competition rules; the development of a Code of Conduct for service providers; and the agreement on procedures for licensing of satellite-based personal communications. The action plan also advocated the possibility of allowing service offerings as a combination of fixed and mobile networks in order to facilitate the full-scale development of personal communications; the lifting of constraints on alternative telecommunications infrastructures and constraints on direct interconnection with other operators; the adoption and implementation of Decisions of the ERC (European Radiocommunications Committee) on frequency bands supporting DCS-1800 and TETRA; the opening up of an Europe-wide Numbering Space for pan-European services including personal communications services; and continuing support of work towards UMTS.

The combination of these regulatory changes will contribute to a substantial acceleration of the EU's mobile communications market and speed the progress towards Third Generation mobile/personal communications. It will however be necessary to encourage potential operators and manufacturers to invest in the required technology, by setting out a clear calendar for the adoption of the required new standards and the re-farming of the necessary spectrum. The applicable licensing regimes and rules for flexible sharing of the available spectrum need also to be adopted at an early stage so as to permit the identification of novel market opportunities commensurate with the broadband multimedia requirements of the Third Generation mobile telecommunications systems.

In light of the above, and in accordance with the political mandate given by the European Parliament and the European Council, the major actors in the mobile and personal communications sector have been brought together as a task force which has lead to the setting up of the UMTS Forum. The main objective of the Forum are to contribute to the elaboration of an European policy for mobile and personal communications based on an industry wide consensus view, and pave the way for ensuring that mobile communications will play a pivotal role in the Global Information Society.

The continued evolution of Second Generation systems has been recognised as an issue of great societal and economic importance for Europe and the European industry. To facilitate and crystallise such an ambition, and in accordance with the political mandate given by the European Parliament and the European Council, an ad-hoc group called the UMTS Task Force was convened by the European Commission and was charged with the task of identifying Europe's mobile communications strategy towards UMTS. The report of the UMTS Task Force and its recommendations have been largely endorsed by the European mobile industry, and as a result the UMTS Forum has now been created with the mandate to provide an on-going high level strategic steer to the further development of European mobile and personal communications technologies. High on the priorities of the UMTS Forum are the issues of technology, spectrum, marketing and regulatory regimes. Drawing participation beyond the European industry, the UMTS Forum is expected to play an important role in bringing into commercial reality the UMTS vision.

Photonic Networks 

In the future, photonics will be able to do many of the same kinds of things as electronics such as amplifying, switching and processing signals. But the key difference is that photonic devices work with optical signals, not electrical signals. This has several advantages, the most important advantage is that photonics can be used to manipulate signals with very high bandwidth (high information content), far beyond the bandwidth limitations of electronics. It is expected that the amount of information carried on computer and

telecommunications networks to continue to grow very rapidly into the future, so photonics will play an important role.

However, most photonic devices (based on non-linear optical effects are still quite primitive in comparison to electronics. It is still early days. Many devices are still confined to research laboratories. The stage of development in photonics today is probably roughly equivalent to the vacuum tube used in the electronic systems of the 1940s.

 

Why use optical signals ?

 

Optics is important because optical fiber cables can be used to transport large amounts of information over very long distances, much more effectively and cheaply than electrical cables or radio. The BT network in the UK alone contains more than 3.5 million kilometres of optical fiber, it is one of the richest optical fiber networks in the world and almost all of BT's long distance telecommunications traffic is carried over optical cables. In a joint venture with six of its partners, BT has recently created the largest pan European high speed network, comprising some 36,000 route kilometres of optical fibers, with points of presence in more than 200 cities across seven countries.

The enormous bandwidth carrying capacity of optical fiber (potentially as great as 10 thousand billion bits per second - equal to about one million simultaneous TV channels) was recognised from the very earliest days of development of optical fiber, more than 30 years ago. However this huge potential capacity has yet to be realised. Today's networks still consist of electronic switches and routers interconnected by point to point optical transmission channels. So in practice, the amount of information that can be carried on one of these channels is not limited by the fiber, but by the information processing speed of the electronic equipment used at each end of the fiber link.

A way round this bottleneck is to carry several optical channels interconnecting several different electronic switching units - simultaneously on the same fiber link. There are two main approaches to doing this. One approach is to use wavelength division multiplexing (WDM) in which data signals on different optical carriers (i.e. different wavelengths, or colours) are combined together on a single fiber. WDM is already at an advanced stage of

development, and point to point links with high aggregate capacity (as great as several hundred billion bits per second) can be deployed today using components and systems that are available commercially.

The other approach to increasing the capacity of fiber systems is to use optical time-division multiplexing (OTDM). OTDM is a method of carrying information on a single channel in the form of ultrashort optical pulses at very high rates - 100 Gbit/s and higher, beyond the envisaged speed limits of electronics. The underlying principle in OTDM is that many lower speed data channels, each transmitted in the form of extremely short optical pulses, are time interleaved to form a single high speed data stream. OTDM is currently viewed as a longer term solution because it relies on different, and much less mature, technologies. Many of the key components needed for OTDM are still confined to the research laboratory. However OTDM has some very important advantages for future photonic networks. Moreover, the two approaches WDM and OTDM are not incompatible, and in the future they will be used in combination to best utilise the fiber bandwidth.

 

So what is a Photonic Network ?

 

The basic approach used to create today's networks - electronic switches interconnected by optical point to point links, has the drawback that all of the information carried on a fiber must be processed and switched using the electronic equipment at the ends of each individual link. But since very often the bulk of the information is passing through in transit to some other network destination, this means that the electronic equipment has to be much bigger and more complex than is really necessary.

But in a new approach currently being developed, data will be transmitted across the future photonic network entirely in the form of optical signals, without the need for big electronic switches. Photonic devices will be used to process and route the information in its optical form. This avoids the need continually to convert optical signals into electronic ones and back again. But even more important, systems based on photonic processing and routing will have the ability to handle much greater volumes of information and at lower cost.

One method of creating a photonic network is to route the optical signals according to their wavelength (e.g. one wavelength for London, another for Paris, and so on). This analogue optical approach to routing signals across a network is very simple, since it requires only passive components such as wavelength filters and gratings, but it has some serious practical limitations.

A more advanced approach is to carry the information across the network in the form of short high speed data packets, in effect a form of OTDM . The information is routed according to the destination address encoded into the packet. This digital optical approach is more akin to the way the routing is

done today using electronics, but ultrafast photonic devices will be used instead. Not only will these signals be routed towards their destination at the speed of light, but they will be regenerated and processed in the optical domain too. It will be possible to transmit these signals over almost infinite distances through great numbers of network nodes without degradation. The digital optical approach thus overcomes the physical limitations of analogue routing, and the information speed of these signals is no longer limited by intermediate electronics. This looks like being a much more efficient and economic way of handling the massive amounts of information that will be carried over communications networks in the future. Moreover there have been recent important advances in the development of ultrafast optical devices that could open up these digital optical techniques to a much wider range of future applications, such as in local area networks and massive capacity routers.

The rapid proliferation of information technology in commerce, finance, education, health, government, security, and home information and entertainment, together with the ever increasing power of computers and data storage devices, is producing a massively increasing demand for network interconnection and traffic. This trend is expected to continue into the future. For example, it is predicted that the processing speed of high end work stations and mass market personal computers will increase by more than 1000 times in the next 10-15 years, and it is predicted that over the same time the traffic demand on core telecommunications networks will grow by at least 100 fold. Photonic networking techniques have the power to satisfy this explosive increase in demand at relatively low cost.

It is becoming increasingly likely that in the longer term, ultrafast photonic techniques, together with wavelength multiplexing, will be used in networks at all levels, from the transcontinental backbone to the desktop.

The Personal Area Network (PAN)

 

Scientists at IBM's Almaden Research Center (San Jose, CA) are perfecting a new Personal Area Network technology (PAN) that uses the natural electrical conductivity of the human body to transmit electronic data.

Using a small prototype transmitter (roughly the size of a deck of cards) embedded with a microchip, and a slightly larger receiving device, the researchers can transmit a preprogrammed electronic business card between two people via a simple handshake. What's more, the prototype allows data to be transmitted from sender to receiver through up to four touching bodies.

 

How PAN works

 

The natural salinity of the human body makes it an excellent conductor of electrical current. PAN technology takes advantage of this conductivity by creating an external electric field that passes an incredibly tiny current through the body, over which is carried.

The current used is one billionth of an amp (one nanoamp), which is lower than the natural currents already in the body. In fact, the electrical field created by running a comb through hair is more than 1,000 times greater than that being used by PAN technology.

The speed at which the data is transmitter is equivalent to a 2400-baud modem. Theoretically, 44 million bits per second could be communicated using this method.

Potential applications

 

IBM researchers envision PAN technology initially being applied in three ways:

To pass simple data between electronic devices carried by two human beings, such as an electronic business card exchanged during a handshake.

To exchange information between personal information and communications devices carried by an individual, including cellular phones, pagers, personal digital assistants (PDAs) and smart cards. For example, upon receiving a page, the number could be automatically uploaded to the cellular phone, requiring the user to simply hit the send button. This automation increases accuracy and safety, especially in driving situations.

To automate and secure consumer business transactions. Among the many examples:

A public phone equipped with PAN sensors would automatically identify the user who would no longer have to input calling card and PINs. This application significantly reduces fraud and makes calling easier and more convenient for users.

By placing RF (radio frequency) sensors on products, such as rental videos, stores could essentially eliminate counter lines and expedite rentals and sales. The customer would simply carry the selected videos through a detecting device that would automatically and accurately identify the customer and his selections, and then bill his account accordingly.

Health service workers could more safely and quickly identify patients, their medical histories and unique medicinal needs by simply touching them. This

application would be particularly helpful in accident situations or where the patients unable to speak or communicate.

In this example, A researcher's electronic business card is transmitted between two people by simply touching fingers.

 

Why use the body to transmit data ?

 

Sharing information increases the usefulness of personal information devices and provides users with features not possible with independent or isolated devices. However, finding a way to do this effectively, securely and cost-efficiently presented a challenge, at least until PAN was developed.

That's because other likely approaches are not practical for everyday use. For example, wiring all these devices together would be cumbersome and constrictive to the user. Infra-red communications of information, used on TV remote controls, requires direct lines of sight to be effective. Radio frequencies (such as those used with automated car locks) could jam or interfere with each other, or be imprecise in crowded situations.

Bluetooth  

Bluetooth technology will allow for the replacement of the many proprietary cables that connect one device to another with one universal short-range radio link. For instance, Bluetooth radio technology when built into both the cellular telephone and the laptop would replace the cumbersome cable used today to connect a laptop to a cellular telephone. Printers, PDA's, desktops, fax machines, keyboards, joysticks and virtually any other digital device can be part of the Bluetooth system. But beyond untethering devices by replacing the cables, Bluetooth radio technology provides a universal bridge to existing data networks, a peripheral interface, and a mechanism to form small private ad hoc groupings of connected devices away from fixed network infrastructures.

Designed to operate in a noisy radio frequency environment, the Bluetooth radio uses a fast acknowledgement and frequency hopping scheme to make the link robust. Bluetooth radio modules avoid interference from other signals by hopping to a new frequency after transmitting or receiving a packet. Compared with other systems operating in the same frequency band, the Bluetooth radio typically hops faster and uses shorter packets. This makes the Bluetooth radio more robust than other systems. Short packages and fast hopping also limit the impact of domestic and professional microwave ovens. Use of Forward Error Correction (FEC) limits

the impact of random noise on long distance links. The encoding is optimised for an uncoordinated environment.

Bluetooth radios operate in the unlicensed ISM band at 2.4 GHz. A frequency hop transceiver is applied to combat interference and fading. A shaped, binary FM modulation is applied to minimise transceiver complexity. The gross data rate is 1Mb/s. A Time Division Duplex scheme is used for full-duplex transmission.

The Bluetooth baseband protocol is a combination of circuit and packet switching. Slots can be reserved for synchronous packets. Each packet is transmitted in a different hop frequency. A packet nominally covers a single slot, but can be extended to cover up to five slots. Bluetooth can support an asynchronous data channel, up to three simultaneous synchronous voice channels, or a channel which simultaneously supports asynchronous data and synchronous voice. Each voice channel supports 64 kb/s synchronous (voice) link. The asynchronous channel can support an asymmetric link of maximally 721 kb/s in either direction while permitting 57.6 kb/s in the return direction, or a 432.6 kb/s symmetric link.

The different functions in the Bluetooth system are:

a radio unit a link control unit link management software functions

The Bluetooth system supports both point to point and point to multi point connections. Several piconets can be established and linked together ad hoc, where each piconet is identified by a different frequency hopping sequence. All users participating on the same piconet are synchronised to this hopping sequence. The topology can best be described as a multiple piconet structure.

The full-duplex data rate within a multiple piconet structure with 10 fully-loaded, independent piconets is more than 6 Mb/s. This is due to a data throughput reduction rate of less than 10% according to system simulations based on 0dBm transmitting power (at the antenna).

xDSL  

DSL (Digital Subscriber Line) is a technology for bringing high-bandwidth information to homes and small businesses over ordinary copper telephone lines. xDSL refers to different variations of DSL, such as ADSL, HDSL, and RADSL. Assuming your home or small business is close enough to a telephone company central office that offers DSL service, you may be able to receive data at rates up to 6.1 megabits (millions of bits) per second (of a

theoretical 8.448 megabits per second), enabling continuous transmission of motion video, audio, and even 3-D effects. More typically, individual connections will provide from 1.544 Mbps to 512 Kbps downstream and about 128 Kbps upstream. A DSL line can carry both data and voice signals and the data part of the line is continuously connected. Compaq, Intel, and Microsoft working with telephone companies have developed a standard and easier-to-install form of ADSL called G.Lite that is accelerating deployment. DSL is expected to replace ISDN in many areas and to compete with the cable modem in bringing multimedia and 3-D to homes and small businesses. Dataquest, a market research firm, forecasts 5.8 million lines installed by the end of 1999.

 

How It Works

 

Traditional phone service (sometimes called "Plain Old Telephone Service" or POTS) connects your home or small business to a telephone company office over copper wires that are wound around each other and called twisted pair. Traditional phone service was created to let you exchange voice information with other phone users and the type of signal used for this kind of transmission is called an analog signal. An input device such as a phone set takes an acoustic signal (which is a natural analog signal) and converts it into an electrical equivalent in terms of volume (signal amplitude) and pitch (frequency of wave change). Since the telephone company's signalling is already set up for this analog wave transmission, it's easier for it to use that as the way to get information back and forth between your telephone and the telephone company. That's why your computer has to have a modem - so that it can demodulate the analog signal and turn its values into the string of 0 and 1 values that is called digital information.

Because analog transmission only uses a small portion of the available amount of information that could be transmitted over copper wires, the maximum amount of data that you can receive using ordinary modems is about 56 Kbps (thousands of bits per second). (With ISDN, which one might think of as a limited precursor to DSL, you can receive up to 128 Kbps.) The ability of your computer to receive information is constrained by the fact that the telephone company filters information that arrives as digital data, puts it into analog form for your telephone line, and requires your modem to change it back into digital. In other words, the analog transmission between your home or business and the phone company is a bandwidth bottleneck.

Digital Subscriber Line is a technology that assumes digital data does not require change into analog form and back. Digital data is transmitted to your computer directly as digital data and this allows the phone company to use a much wider bandwidth for transmitting it to you. Meanwhile, if you choose, the signal can be separated so that some of the bandwidth is used to transmit an analog signal so that you can use your telephone and computer on the same line and at the same time.

Splitter-based vs. Splitterless DSL

 

Most DSL technologies require that a signal splitter be installed at a home or business, requiring the expense of a phone company visit and installation. However, it is possible to manage the splitting remotely from the central office. This is known as splitterless DSL, DSL Lite, G.Lite, or Universal ADSL and has recently been made a standard.

 

Modulation Technologies

 

Several modulation technologies are used by various kinds of DSL, although these are being standardised by the International Telecommunication Union (ITU). Different DSL modem makers are using either Discrete Multitone Technology (DMT) or Carrierless Amplitude Modulation (CAP). A third technology, known as Multiple Virtual Line (MVL), is another possibility.

 

Factors Affecting the Experienced Data Rate

 

DSL modems follow the data rate multiples established by North American and European standards. In general, the maximum range for DSL without repeaters is 5.5 km (18,000 feet). As distance decreases toward the telephone company office, the data rate increases. Another factor is the gauge of the copper wire. The heavier 24 gauge wire carries the same data rate farther than 26 gauge wire. If you live beyond the 5.5 kilometer range, you may still be able to have DSL if your phone company has extended the local loop with optical fiber cable.

The Digital Subscriber Line Access Multiplexer (DSLAM)

 

To interconnect multiple DSL users to a high-speed backbone network, the telephone company uses a Digital Subscriber Line Access Multiplexer (DSLAM). Typically, the DSLAM connects to an asynchronous transfer mode (ATM) network that can aggregate data transmission at gigabit data rates. At the other end of each transmission, a DSLAM demultiplexes the signals and forwards them to appropriate individual DSL connections.

 

Types of DSL

ADSL

The variation called ADSL (Asymmetric Digital Subscriber Line) is the form of DSL that will become most familiar to home and small business users. ADSL is called "asymmetric" because most of its two-way or duplex bandwidth is devoted to the downstream direction, sending data to the user. Only a small portion of bandwidth is available for upstream or user-interaction messages. However, most Internet and especially graphics- or multi-media intensive Web data need lots of downstream bandwidth, but user requests and responses are small and require little upstream bandwidth. Using ADSL, up to 6.1 megabits per second of data can be sent downstream and up to 640 Kbps upstream. The high downstream bandwidth means that your telephone line will be able to bring motion video, audio, and 3-D images to your computer or hooked-in TV set. In addition, a small portion of the downstream bandwidth can be devoted to voice rather data, and you can hold phone conversations without requiring a separate line.

Unlike a similar service over your cable TV line, using ADSL, you won't be competing for bandwidth with neighbors in your area. In many cases, your existing telephone lines will work with ADSL. In some areas, they may need upgrading.

 

CDSL

CDSL (Consumer DSL) is a trademarked version of DSL that is somewhat slower than ADSL (1 Mbps downstream, probably less upstream) but has the advantage that a "splitter" does not need to be installed at the user's end. CDSL uses its own carrier technology rather than DMT or CAP ADSL technology.

 

G.Lite or DSL Lite

G.Lite (also known as DSL Lite, splitterless ADSL, and Universal ADSL) is essentially a slower ADSL that doesn't require splitting of the line at the user end but manages to split it for the user remotely at the telephone company. G.Lite, officially ITU-T standard G-992.2, provides a data rate from 1.544 Mbps to 6 Mpbs downstream and from 128 Kbps to 384 Kbps upstream. G.Lite is expected to become the most widely installed form of DSL.

 

HDSL

The earliest variation of DSL to be widely used has been HDSL (High bit-rate DSL) which is used for wideband digital transmission within a corporate site and between the telephone company and a customer. The main characteristic of HDSL is that it is symmetrical: an equal amount of bandwidth is available in

both directions. For this reason, the maximum data rate is lower than for ADSL. HDSL can carry as much on a single wire of twisted-pair as can be carried on a T1 line in North America or an E1 line in Europe (2,320 Kbps).

 

RADSL

RADSL (Rate-Adaptive DSL) is an ADSL technology from Westell in which software is able to determine the rate at which signals can be transmitted on a given customer phone line and adjust the delivery rate accordingly. Westell's FlexCap2 system uses RADSL to deliver from 640 Kbps to 2.2 Mbps downstream and from 272 Kbps to 1.088 Mbps upstream over an existing line.

 

SDSL

SDSL (Symmetric DSL) is similar to HDSL with a single twisted-pair line, carrying 1.544 Mbps (U.S. and Canada) or 2.048 Mbps (Europe) each direction on a duplex line. It's symmetric because the data rate is the same in both directions.

 

UDSL

UDSL (Unidirectional DSL) is a proposal from a European company. It's a unidirectional version of HDSL.

 

VDSL

VDSL (Very high data rate DSL) is a developing technology that promises much higher data rates over relatively short distances (between 51 and 55 Mbps over lines up to 1,000 feet or 300 meters in length). It's envisioned that VDSL may emerge somewhat after ADSL is widely deployed and co-exist with it. The transmission technology (CAP, DMT, or other) and its effectiveness in some environments is not yet determined. A number of standards organizations are working on it.

 

x2/DSL

x2/DSL is a modem from 3Com that supports 56 Kbps modem communication but is upgradeable through new software installation to ADSL when it becomes available in the user's area. 3Com calls it "the last modem you will ever need."

HTTP - The Next Generation

 

The World Wide Web is a tremendous and growing success and HTTP has been at the core of this success as the primary substrate for exchanging information on the Web. However HTTP 1.1 is becoming strained modularity wise as well as performance wise and those problems are to be addressed by HTTP-NG.

Modularity is an important kind of simplicity, and HTTP 1.x isn't very modular. If we look carefully at HTTP 1.x, we can see it addresses three layers of concerns, but in a way that does not cleanly separate those layers: message transport, general-purpose remote method invocation, and a particular set of methods historically focused on document processing (broadly construed to include things like forms processing and searching).

The lack of modularity makes the specification and evolution of HTTP more difficult than necessary and also causes problems for other applications. Applications are being layered on top of HTTP, and these applications are thus forced to include a lot of HTTP's design, whether this is technically ideal or not. Furthermore, to avoid some of the problems associated with layering on top of HTTP, other applications start by cloning a subset of HTTP and layering on top of that.

The HTTP-NG protocol is a new architecture for the Web infrastructure based on a layered approach where HTTP is split up in layers as depicted in the diagram below:

 

Multiple data streams

 

The single HTTP-NG connection is divided up into multiple virtual sessions, each of which can carry a requested object in parallel. These are asynchronous, so a client can fire off multiple requests without waiting for the request to be acknowledged, let alone wait for the object to be sent.

There is a dedicated control session, similar in application to the separate control connection in the FTP protocol, which is used to send all the requests and to receive meta information (author, copyright details, costs, or redirection requests to use a special external connection, for example for live video over an ATM link).

Binary protocol

 

HTTP is a text based protocol. This makes it easy to debug. However all those text headers means that there is considerable overhead when transporting small objects around. The transport is 8 bit capable, so it could cope with binary data and indeed does so for the object bodies. Only the headers are text based.

HTTP-NG uses a binary protocol, encoded in ASN.1 and made even more compact by using Packed Encoding Rules (PER). What this means is that a typical request is very small, but looks like random garbage until you decode it.

 

Authentication and charging

 

Each individual message within an HTTP-NG connection can be authenticated. The security method is not part of the protocol, so any method that both the client and the server support can be used, individual messages can use different authentication schemes if needed. The encrypted data can be securely carried across untrusted intermediate proxies.

Related to the challenge response model of authentication, a server can notify a client that a requested service will incur a fee, sending the cost and a list of acceptable payment methods.

 

Transition strategies

 

The current status of HTTP-NG is as an experimental prototype. It has been tested between a pair of machines over a transatlantic link, and shown to perform well, utilising the entire available bandwidth. In contrast, HTTP 1,0 was only able to effectively use around a tenth of the available bandwidth. As predicted, the performance of HTTP-NG did not degrade as badly as HTTP in congested conditions, it performed significantly better than multiple concurrent connections such as would be made by a modern multithreaded browser.

All initial HTTP-NG requests are also valid HTTP 1.0 requests, but use an invalid access method. This means that an HTTP-NG enabled client can initiate a request with a server and continue it with HTTP-NG (if that is supported) or receive an error response and try again with HTTP 1.0 on the same port.

The easiest way to transition towards HTTP-NG would be for well connected proxy servers to talk using HTTP-NG over potentially congested links such as the transatlantic links and the link to continental Europe. These proxy servers would accept the HTTP 1.0 protocol, and convert responses to HTTP 1.0, they would also be able to use HTTP-NG to talk to newer clients and servers. It has also been suggested that a proxy server could analyse incoming HTML documents and prefetch all the inline images with one HTTP-NG request in anticipation of their being needed.

XML And The Future Web  

The extraordinary growth of the World Wide Web has been fueled by the ability it gives authors to easily and cheaply distribute electronic documents to an international audience. As Web documents have become larger and more complex, however, Web content providers have begun to experience the limitations of a medium that does not provide the extensibility, structure, and data checking needed for large-scale commercial publishing. The ability of Java applets to embed powerful data manipulation capabilities in Web clients makes even clearer the limitations of current methods for the transmittal of document data.

To address the requirements of commercial Web publishing and enable the further expansion of Web technology into new domains of distributed document processing, the World Wide Web Consortium has developed an Extensible Markup Language (XML) for applications that require functionality beyond the current Hypertext Markup Language (HTML).

 

Background: HTML and SGML

 

Most documents on the Web are stored and transmitted in HTML. HTML is a simple language well suited for hypertext, multimedia, and the display of small and reasonably simple documents. HTML is based on SGML (Standard Generalized Markup Language, ISO 8879), a standard system for defining and using document formats.

SGML allows documents to describe their own grammar -- that is, to specify the tag set used in the document and the structural relationships that those tags represent. HTML applications are applications that hardwire a small set of tags in conformance with a single SGML specification. Freezing a small set of tags allows users to leave the language specification out of the document and makes it much easier to build applications, but this ease comes at the cost of severely limiting HTML in several important respects, chief among which are extensibility, structure, and validation.

Extensibility. HTML does not allow users to specify their own tags or attributes in order to parameterise or otherwise semantically qualify their data.

Structure. HTML does not support the specification of deep structures needed to represent database schemas or object-oriented hierarchies.

Validation. HTML does not support the kind of language specification that allows consuming applications to check data for structural validity on importation.

In contrast to HTML stands generic SGML. A generic SGML application is one that supports SGML language specifications of arbitrary complexity and makes possible the qualities of extensibility, structure, and validation missing from HTML. SGML makes it possible to define your own formats for your own documents, to handle large and complex documents, and to manage large information repositories. However, full SGML contains many optional features that are not needed for Web applications and has proven to have a cost/benefit ratio unattractive to current vendors of Web browsers.

 

The XML effort

 

The World Wide Web Consortium (W3C) has created an SGML Working Group to build a set of specifications to make it easy and straightforward to use the beneficial features of SGML on the Web. The goal of the W3C SGML activity is to enable the delivery of self-describing data structures of arbitrary depth and complexity to applications that require such structures.

The first phase of this effort is the specification of a simplified subset of SGML specially designed for Web applications. This subset, called XML (Extensible Markup Language), retains the key SGML advantages of extensibility, structure, and validation in a language that is designed to be vastly easier to learn, use, and implement than full SGML.

XML differs from HTML in three major respects:

1. Information providers can define new tag and attribute names at will. 2. Document structures can be nested to any level of complexity. 3. Any XML document can contain an optional description of its grammar

for use by applications that need to perform structural validation.

XML has been designed for maximum expressive power, maximum teachability, and maximum ease of implementation. The language is not backward-compatible with existing HTML documents, but documents conforming to the W3C HTML 3.2 specification can easily be converted to XML, as can generic SGML documents and documents generated from databases.

 

Web applications of XML

 

The applications that will drive the acceptance of XML are those that cannot be accomplished within the limitations of HTML. These applications can be divided into four broad categories:

1. Applications that require the Web client to mediate between two or more heterogeneous databases.

2. Applications that attempt to distribute a significant proportion of the processing load from the Web server to the Web client.

3. Applications that require the Web client to present different views of the same data to different users.

4. Applications in which intelligent Web agents attempt to tailor information discovery to the needs of individual users.

The alternative to XML for these applications is proprietary code embedded as "script elements" in HTML documents and delivered in conjunction with proprietary browser plug-ins or Java applets. XML derives from a philosophy that data belongs to its creators and that content providers are best served by a data format that does not bind them to particular script languages, authoring tools, and delivery engines but provides a standardised, vendor-independent, level playing field upon which different authoring and delivery tools may freely compete.

Web agents: data that knows about me

 

A future domain for XML applications will arise when intelligent Web agents begin to make larger demands for structured data than can easily be conveyed by HTML. Perhaps the earliest applications in this category will be those in which user preferences must be represented in a standard way to mass media providers.

Consider a personalised TV guide for the fabled 500-channel cable TV system. A personalised TV guide that works across the entire spectrum of possible providers requires not only that the user's preferences and other characteristics (educational level, interest, profession, age, visual acuity) be specified in a standard, vendor-independent manner -- obviously a job for an industry-standard markup system -- but also that the programs themselves be described in a way that allows agents to intelligently select the ones most likely to be of interest to the user. This second requirement can be met only by a standardised system that uses many specialised tags to convey specific attributes of a particular program offering (subject category, audience category, leading actors, length, date made, critical rating, specialised content, language, etc.). Exactly the same requirements would apply to customised newspapers and many other applications in which information selection is tailored to the individual user.

While such applications still lie over the horizon, it is obvious that they will play an increasingly important role in our lives and that their implementation will require XML-like data in order to function interoperably and thereby allow intelligent Web agents to compete effectively in an open market.

 

Advanced linking and stylesheet mechanisms

 

Outside XML as such, but an integral part of the W3C SGML effort, are powerful linking and stylesheet mechanisms that go beyond current HTML-based methods just as XML goes beyond HTML.

Despite its name and all of the publicity that has surrounded HTML, this so-called "hypertext markup language" actually implements just a tiny amount of the functionality that has historically been associated with the concept of hypertext systems. Only the simplest form of linking is supported -- unidirectional links to hardcoded locations. This is a far cry from the systems that were built and proven during the 1970s and 1980s.

In a true hypertext system of the kind envisioned for the XML effort, there will be standardised syntax for all of the classic hypertext linking mechanisms:

Location-independent naming Bidirectional links Links that can be specified and managed outside of documents to which

they apply N-ary hyperlinks (e.g., rings, multiple windows) Aggregate links (multiple sources) Transclusion (the link target document appears to be part of the link

source document) Attributes on links (link types)

 

Stylesheets

 

The current CSS (cascading style sheets) effort provides a style mechanism well suited to the relatively low-level demands of HTML but incapable of supporting the greatly expanded range of rendering techniques made possible by extensible structured markup. The counterpart to XML is a stylesheet programming language that is:

Freely extensible so that stylesheet designers can define an unlimited number of treatments for an unlimited variety of tags.

Turing-complete so that stylesheet designers can arbitrarily extend the available procedures.

Based on a standard syntax to minimise the learning curve. Able to address the entire tree structure of an XML document in

structural terms, so that context relationships between elements in a document can be expressed to any level of complexity.

Completely internationalised so that left-to-right, right-to-left, and top-to-bottom scripts can all be dealt with, even if mixed in a single document.

Provided with a sophisticated rendering model that allows the specification of professional page layout features such as multiple column sets, rotated text areas, and float zones.

Defined in a way that allows partial rendering in order to enable efficient delivery of documents over the Web.

Such a language already exists in a new international standard called the Document Style Semantics and Specification Language (DSSSL, ISO/IEC 10179). Published in April, 1996, DSSSL is the stylesheet language of the future for XML documents.

HTML functions well as a markup for the publication of simple documents and as a transportation envelope for downloadable scripts. However, the need to support the much greater information requirements of standardised Java applications will necessitate the development of a standard, extensible, structured language and similarly expanded linking and stylesheet mechanisms. The W3C SGML effort is actively developing a set of specifications that will allow these objectives to be met within an open standards environment.

WAP 

Handheld devices are more limited than desktop computers in several important ways. Their screens are small, perhaps a few inches square or able to display only a few lines of text, and they’re often monochrome instead of colour. Their input capabilities are limited to a few buttons or numbers, or entering data takes extra time, as happens with a personal digital assistant’s

(PDA) handwriting recognition capabilities. They have less processing power and memory to work with, and their wireless network connections have less bandwidth and are slower than those of computers hard wired to fast LANs.

The Wireless Application Protocol (WAP) was designed to make it easier to create networked applications for handheld devices despite those drawbacks. WAP is a standardisation effort by the Wireless Application Protocol Forum, an industry association comprising more than 200 vendors of wireless devices, services and tools. The goal of the WAP Forum is to provide a set of specifications that allow developers to write Internet enabled applications that run on small form factor, wireless devices. Typically, these devices are smart phones, pagers and PDAs.

The Problems With HandheldsA handheld’s constraints mean that it’s usually impossible to directly port a desktop application to a wireless handheld device. For the same reasons, it’s difficult to directly access most Web sites with a handheld device. Web applications are traditionally designed based on the assumption that visitors will have a desktop computer with a large screen and a mouse. A smart phone can’t display a large colour graphic and doesn’t have point and click navigation capabilities. Programmers need to rewrite applications, taking into account the limitations of these devices, and design Web sites so that handheld users can access them.

But the handheld device market consists of many different devices running on competing operating systems: 3Com`s Palm OS, Symbian`s EPOC operating system, Microsoft’s Windows CE, Motorola’s FlexOS, Microware Systems Corp`s OS-9 and Sun’s Java. Handheld applications also need to run over a variety of wireless network architectures, such as Cellular Digital Packet Data (CDPD), Code Division Multiple Access (CDMA), Global System for Mobile Communications (GSM), Personal Digital Cellular (PDC), Personal Handyphone System (PHS), time division multiple access (TDMA), Flex (Motorola’s one-way paging protocol), ReFlex (Motorola’s two-way paging protocol), Integrated Digital Enhanced Network (iDEN), Tetra, Digital Enhanced Cordless Telecommunications (DECT), DataTAC (an advanced radio data information service network) and the Mobitex RAM mobile data network. In order to create a common programming environment that would let a developer write one application that runs on multiple devices and networks, the WAP Specification Suite was born.

Think of it as the IBM PC of the mobile world, it’s the single spec that everyone can write to. Instead of having tiny little islands of mobile information, any user with any handset can access information.

The WAP Forum isn’t a standards body, but it does work with international standards organisations and offers its specifications for official recognition.What makes WAP work as a de facto standard is that the major players in the wireless market all support the specification.

WAP is important because more and more information is going out over the

wireless network. Recent IDC reports predict that sales of smart phones, just one type of device that supports WAP — will reach 539 million units worldwide in 2003.

The WAP Forum has a three stage, public- omment process for including wireless standards specifications in its WAP Specification Suite, now at Version 1.1.