jozef goetz, 2015 1 © 2007-15 pearson education expanded by j. goetz, 2015 credits: parts of the...
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Jozef Goetz, 2015
1
© 2007-15 Pearson Education
Expanded by J. Goetz, 2015
Credits: Parts of the slides are based on slides created by textbook authors, B.A Forouzan published by The McGraw-Hill Companies, Inc. and A. S. Tanenbaum published by Printice Hall
Jozef Goetz, 2015
Saying 2
The whole problem with the world is that fools and fanatics are always so certain of themselves, but wiser people so full of doubts.
- Bertrand Russell
Jozef Goetz, 2015
3Learning outcomes In this chapter, you will learn about:
The different types of programming languages.
The evolution of the Internet, Internet standards organizations, and the difference between the Internet, intranets, and extranets.
The beginning of the World Wide Web, ethical use of information on the Web, Web Accessibility, and future Internet trends.
The Client/Server Model,
Internet Protocols,
Networks,
URLs and
Domain Names, and Markup Languages.
Jozef Goetz, 2015
4Machine Languages, Assembly Languages and High Level Languages
Programming Languages Hundreds exist today Fall into three categories
1. Machine languages– “Natural language” of computer component– Machine dependent
2. Assembly languages– English-like abbreviations represent computer operations– Translator programs convert to machine language
3. High-level languages– Allows for writing more “English-like” instructions
• Contains commonly used mathematical operations– Compiler converts to machine language at the begining
– Interpreter• Execute high-level language programs without compilation
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5 Machine Languages, Assembly
Languages and High Level Languages (II) Machine Languages
Only language understood directly by computer Defined by computer’s hardware design
Machine-dependent– Languages specific to particular computers
Difficult to understand for human Example:
+1300042774+1400593419+1200274027
Streams and numbers– Ultimately reduced to 0s and 1s
• Binary code– Instruct most elementary of operations
Slow, tedious and error-prone– Led to Assembly languages
Jozef Goetz, 2015
6 Machine Languages, Assembly
Languages and High Level Languages (III)
Assembly Languages Example:
LOAD BASEPAYADD OVERPAYSTORE GROSSPAY
English-like abbreviations Represent elementary operations of computer
Translated to machine language Assemblers convert to machine language High-speed conversion
More clear to human readers Still tedious to use
– Many instructions for simple tasks– Led to high-level languages
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7
High-level languages (II) Much more desirable from programmer’s standpoint Specific languages include
C, C++, Visual Basic.NET, C# and Java Among most powerful and widely used languages today Those languages use compilers.
In this book, several key scripting programming languages JavaScript, ActionScript, PHP and Ruby on Rails —each of these scripting
languages is processed by interpreters
Interpreter programs developed to execute high-level programs without compiling
Popular in program development environments interpret each statement separately versus all statements at once
Once program developed, compiled version made
Study markup languages HTML/XHTML and XML, which can be processed by interpreted scripting
languages Achieve their goal of portability across a variety of platforms
Machine Languages, Assembly Languages and High Level Languages
Jozef Goetz, 2015
8 C, C++, Visual Basic .NET and Java C - 1972
Developed by Dennis Ritchie Evolved from the B language (“typelless” – every data occupied one word)
at Bell Labs Kernighan and Ritchie: “The C Programming Language”.’78, 2nd ’88
ANSI/ISO 9899 established worldwide standards for C programming called ANSI C Added data type features
Gained recognition as language of UNIX Now a widely used language
Available on most computers Language of most major operating systems Led to development of C++
Portable to most computers, input/output instructions different for different operating systems
Jozef Goetz, 2015
9 C, C++, Visual Basic .NET and Java (II)
C++ - 1980 Developed by Bjarne Stroustrup
(a Danish computer scientist) at Bell Labs (1980s) Extension of C
Uses elements from Simula 67
– Simulation programming language Provides features to “spruce up” C
Provides Object-oriented technology
– Hybrid language
• structured programming
• object-oriented programming (OOP)
• possible to use both
Jozef Goetz, 2015
10C, C++, Visual Basic .NET and Java (IV) VISUAL BASIC- mid 1960s
Based from BASIC (mid 1960s) Beginners All-Purpose Symbolic Instruction Code Implemented by Bill Gates at Microsoft
BASIC evolved to Visual Basic Resulting from Windows GUI (late 1980s early 1990s)
– Graphical User Interface Included capabilities such as
– object based programming,– error handling and – GUI creation
Evolved to .NET – fully Object Oriented Programming language Allows access to .NET libraries Improved object oriented programming
Jozef Goetz, 2015
11 C, C++, Visual Basic .NET and Java
(V) Java 1991 - announced in 05/1995 Sun Microsystems corporate research project (1991)
Code-named Green Based on C and C++ Intended for intelligent consumer-electronic devices
Lack of popularity almost causes cancellation Sudden popularity of WWW in 1993 provided new potential
Used Java to create web pages with dynamic content (java applets)– Animated and interactive content
Grabbed attention of business community Now very widely used
Enhance functionality of WWW servers Provide applications for consumer devices (pagers, cell phones, PDAs,…)
Java programs Consist of pieces called classes Classes contain methods, which perform tasks
Jozef Goetz, 2015
12 C# C#
Developed at Microsoft by a team led by Anders Hejlsberg and Scott Wiltamuth
Event driven, object oriented, visual programming language Roots in C, C++ and Java Used to develop windows, Web services, Web-based apps and mobile
apps (cell phones: Windows Phone 8 and iPhone using MonoTouch)
Incorporated into .NET platform Web based applications can be distributed
– Devices and desktop computers Programs that can be accessed by anyone through any device Allows communicating with applications written in different languages
Visual Studio - Integrated Design Environment (IDE) Makes programming and debugging fast and easy The process of rapidly creating an application using an IDE is referred
to as Rapid Application Development (RAD)
Jozef Goetz, 2015
13Why C# ? The integration of software components from various languages proved
difficult, and installation problems were common new versions of shared components were incompatible with old
software – it led to include Common Language Specification (CLS) in .NET framework with C# as a primary language
Developers recognized the need for software that was accessible to anyone and available from almost any type of device!!!
C# is fundamental language and design specifically for the .NET Microsoft key technologies and Windows, Web Services and Distributed Applications.
It has roots in C, C++ and Java, adapting the best features of each and adding new features of its own
Power of C with ease of Microsoft Visual Basic® Much cleaner than C++ More structured than Visual Basic More powerful than Java for small and medium size apps.
Jozef Goetz, 2015
14The Evolution of the Internet
Internet Is a public, globally Interconnected network of computer
networks
• When 2 or more networks are connected, they become an internetwork, or internet.
• An internet is a network of networks. • An "internet" (lower case i) is any computers connected to each other (a
network), and are not part of the Internet unless the use TCP/IP protocols.
• The Internet (upper case) is a collaboration of more
than 100s thousands interconnected networks. INTERNET (Upper case I) The vast collection of interconnected networks that all
use the TCP/IP protocols and that evolved from the ARPANET of the late 60’s and early 70’s.
Jozef Goetz, 2015
15A brief history of the Internet.
• ARPANET (50s and 60s, some universities)
• NSFNET (late 70s, all universities)
• TCP/IP (invention ’74) became the official protocol in 1983. When NSFNET and the ARPANET were connected, the growth became
exponential Many regional networks (Canada, Europe, the Pacific) joined up In mid-80s people began viewing the collection of networks as the Internet The glue that holds the Internet together is the TCP/IP reference model and
TCP/IP protocol stack
• ANS (Advanced Networks and Service) by MERIT, MCI, and IBM took over NSFNET in 1990 and form ANSNET
• ANSNET sold to American Online in 1995.
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16Intranet & Extranets
Intranet A private network contained within an organization or business
used to share information and resources among coworkers. An intranet may be on the Internet or may simply be a network
Extranet A private network that securely shares part of an organization’s
information or operations with external partners. It uses the same protocols as the Internet.
Use of the Internet was originally limited to government, research and academic use
1991 Commercial ban lifted
Jozef Goetz, 2015
17The ARPANET
Growth of the ARPANET (a) December 1969. (b) July 1970. (c) March 1971. (d) April 1972. (e) September 1972.
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18
•End users to be connected use the services of Internet Service Provider (ISP)
NAP = Network Access Point to the Internet Backbonein major cities, •is the complex switching stations.
Speed: up to 600 Mbps
National hierarchical organization of the Internet
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•End users to be connected use the services of Internet Service Provider (ISP)
There are local, regional, national, and international Internet service providers (ISPs).
NAP = Network Access Point to the Internet Backbone(very high-speed connectivity)in major cities,•is the complex switching stations.
Speed: up to 600 Mbps Internet Backbone A high capacity communication link that carries data gathered from smaller links that interconnect with it.
NAP – Network Access Point Access points or
junctions to the Internet Backbone in major cities.
International hierarchical organization of the Internet
Jozef Goetz, 2015
20Growth of Internet
Hobbes Internet Timeline http://www.zakon.org/robert/internet/timeline/
Jozef Goetz, 2015
21Growth of Internet Hobbes Internet Timeline
http://www.zakon.org/robert/internet/timeline/ www Growth
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Growth of the Internet
http://www.internetworldstats.com/stats.htm
22Copyright © Terry Felke-Morris
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23Internet Usage
Traditional applications (1970 – 1990) E-mail
News • newsgroups devoted to different topics
Remote login • Using telnet, rlogin, ssh programs
File transfer• Using FTP programs
Jozef Goetz, 2015
24Internet Usage In ’90 Tim Berners-Lee at CERN (Switzerland) invented
the WWW (World Wide Web)
Tim Berners-Lee Developed information system based on hyperlinked text
documents– Berners-Lee called his invention the HyperText Markup Language
(HTML)• allows computer users to locate and view multimedia-based
documents – He developed communication protocols HyperText Transfer Protocol
(HTTP) as backbone
WWW today Makes info instantly accessible Merges computing and communication technologies
Jozef Goetz, 2015
25Internet Usage
In ’93 development of Mosaic by Marc Anderson, the first graphics-based web browser at NCSA
This created an interface to the Web that was easy to use – just point and click instead of remembering text commands
This set the stage for easier information sharing and retrieval
The ch-r of the network was changed from an academic and military playground to a public utility
Jozef Goetz, 2015
26Reasons for Internet Growth
1. Development of the World Wide Web – WWW by Tim Berners-Lee at CERN
The graphical user interface GUI to information stored on some of the computers connected to the Internet
2. Development of Mosaic, the first graphics-based web browser at NCSA
3. Removal of the ban on commercial activity in ‘91 This set the stage for e-commerce
Jozef Goetz, 2015
27Internet Standards & Coordination The Internet Society
No single person “in charge” of the Internet instead infrastructure standards are overseen by A professional organization that provides leadership in addressing
issues related to the future of the Internet
IETF - Internet Engineering Task Force RFC – Requests for Comments publication
– The final version becomes the Internet standard
IAB – Internet Architecture Board is a committee of IETF
ICANN – ’98 a nonprofit organization The Internet Corporation for Assigned Numbers & Names Non-profit organization whose main function is to coordinate the assignment
of
– Internet domain names, – IP address numbers, – protocol parameters, and – protocol port numbers.
Jozef Goetz, 2015
28Web Standards and the W3C Consortium
W3C – World Wide Web Consortium www.w3.org
takes a proactive role in developing recommendations and prototype technologies related to the Web
produces specifications, called Recommendations, in an effort to standardize web technologies
Jozef Goetz, 2015
29Web Accessibility WAI – Web Accessibility Initiative
www.w3.org/WAI Is a major area of work by the W3C Develops recommendations (taking users with challenges into consideration as
well) for – web content developers, – web authoring tool developers, – developers of web browsers, and – developers of other user agents to facilitate use of the web by those with
special needs.
WCAG -Web Content Accessibility Guidelineshttp://www.w3.org/WAI/WCAG20/quickref/
Section 508 of the Rehabilitation Act ’98 www.section508.gov requires that government agencies must give individuals with disabilities
access to information technology that is comparable to the access available to others
Jozef Goetz, 2015
ISO (International Standards Organization) 1946 – vast number of subjects
89 countries 13000 standards ISO is a member of ITU-T Documents are:
– Draft– Draft International– International Standard
ANSI (American National Standards Institute) Private, nongovernmental, nonprofit organization
NIST (National Institute of Standards and Technology) – a part of the US Dept of Commerce
IEEE (Institute of Electrical and Electronics Engineering) Largest professional organization in the world
ITU-T International Telecommunications Union - Telecommunications Standardization Sector (former CCITT) – 3000 recommendations
OrganizationsOrganizations
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Federal Communication Commission (FCC) Authority for interstate and international traffic
Reviews communication services and prices Reviews technical specs of communication hardware Assigns carrier frequencies for radio and television
Public Utility Commission (PUC) Authority for intrastate traffic
RReegulatory Agenciesgulatory Agencies
Jozef Goetz, 2015
32Checkpoint 1.1 1. Describe the difference between the
Internet and an intranet. 2. Explain 3 events that contributed to the
commercialization and exponential growth of the Internet.
3. Describe the difference between the Internet and the Web. Internet - a global, interconnected network of computer
networks The World Wide Web is a graphical user interface GUI
that provides access to the info available on the Internet; a system of Internet servers that support specially HTML
formatted documents. the Web is a system of clients (Web browsers) and servers that uses the Internet
for its data exchange The Web is a subset of the Internet.
From the Free Online Dictionary of Computing, we get this definition from its entry for WWW:
"An Internet client-server hypertext distributed information retrieval system
Jozef Goetz, 2015
33Network Overview
Network -- two or more computers connected together for the purpose of communicating and sharing resources
Jozef Goetz, 2015
34 Categories of networks
A network falls is determined by criteria:1. Its size2. Its ownership3. The distance
Jozef Goetz, 2015
35Networks
LAN -- Local Area Network Usually confined to a single building or group of
buildings
MAN -- Metropolitan Area Network Connects computer resources in a local geographical
area e.g. city
WAN -- Wide Area Network Usually uses some form of public or commercial
communications network to connect computers is widely dispersed geographical areas e.g. regions, countries, states, with a minimum distance typical of that between major metropolitan areas.
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LAN - Local Area Network
•Designed for a single office, campus, building or between nearby buildings. •LANs allow resources to be shared
•Hardware•Software•Data
between PCs or workstations.
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LAN
A given LAN use only one type of transmission medium.
Speed : 4-16 MbpsToday: 10 Gbps
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MAN Metropolitan Area Network (e.g. cable TV)
Designed to extend over an entire city, connects LANs
LANs can be shared
- offices can be connected via a city
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WAN - Wide Area Network
Provides all transmission (data, video, image etc.) over large areas e.g. states, countries, a continent , or the whole world.
Usually uses some form of public or commercial communications network to connect computers is widely dispersed geographical areas e.g. regions, countries, states, with a minimum distance typical of that between major metropolitan areas.In contrast to LANs may utilize public, leased, or private communication equipment.
Jozef Goetz, 2015
40A WAN connecting two LANs
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41
A heterogeneous network made of four WANs and two LANs
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42Wide Area Networks
Relation between hosts on LANs and the subnet. The subnet consists of routers and transmission lines.
A router is a specialized piece of switching hardware that is responsible for determining the direction that data packets should be sent.
Routers are responsible for directing data down transmission lines from one LAN to another.
Jozef Goetz, 2015
43Wide Area Networks
A stream of packets from sender to receiver. A subnet is organized according to the principle called store-and-forward or
packet-switched subnet
– The message sent by a process is broken down into smaller packets to send.– Each packet is sent out onto the network.– As a packet arrives at a router, it is stored (store-and-forward) there until the outgoing
line is free. It is then sent on it’s way.– All the packets (of the same message) make take the same or different routes depending
on if they are individually routed or not.
Jozef Goetz, 2015
44The Client/Server Model
Client/Server can describe a relationship between two computer programs – the "client" and the "server".
The Internet Client/Server Model Client -- Web Browser Server -- Web Server
Jozef Goetz, 2015
45The Client/Server Model
Client requests some type of service (such
as a web page, file or database access) from the server.
Server fulfills the request and transmits the
results to the client over a network
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46Web Client
Connected to the Internet when needed
Usually runs web browser (client) software such as Internet Explorer, Mozilla, Opera, Safari, Chrome or Netscape Uses HTTP (Hypertext Transfer Protocol)
Requests web pages from server Receives web pages and files from server
Jozef Goetz, 2015
47Web Server
Continually connected to the Internet
Runs web server software (such as Apache or Internet Information Server)
Uses HTTP (Hypertext Transfer Protocol)
Receives request for the web page
Responds to request and transmits status code, web page, and associated files
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48 Client / Server
1. Continually connected to the Internet
2. Runs web server software such as Apache or Internet
Information Server
3. Uses HTTP (Hypertext Transfer Protocol)
4. Receives request for the web page
5. Responds to request and transmits status code, web page, and associated files
1. Connected to the Internet when needed
2. Usually runs web browser (client) software such as Internet Explorer, Mozilla,
Opera, Safari, Chrome or Netscape
3. Uses HTTP (Hypertext Transfer Protocol)
4. Requests web pages from server
5. Receives web pages and files from server
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49Internet Protocols
Protocols are rules that describe the methods (operations)
used for clients and servers to communicate with each other over a network.
There is no single protocol that makes the Internet and Web work a # of protocols with specific functions are needed.
Jozef Goetz, 2015
50MIME Type
Multi-Purpose Internet Mail Extension (MIME read:maim) A communications protocol (a set of rules) that allows
exchange 7 different media types (multimedia documents), such as audio video image application message multipart text
to be exchanged among many different computer systems
The web browser uses the MIME type to determine how to display the document text/html type is the MIME type of a Web page image/gif or image/jpeg is the MIME type of gif
Jozef Goetz, 2015
51FTP File Transfer Protocol
A set of rules that allow files to be exchanged between computers on the Internet.
Web developers commonly use FTP to transfer web page files from their computers to web servers.
FTP is also commonly used to download programs and files from other servers to individual computers.
Jozef Goetz, 2015
52E-mail Protocols
Sending E-mailSMTP - Simple Mail Transfer
Protocol
Receiving E-mailPOP (POP3) - Post Office Protocol IMAP - Internet Mail Access
Protocol
Jozef Goetz, 2015
53HTTP - Hypertext Transfer Protocol
A set of rules for exchanging files such as text, graphic images, sound, video,
and other multimedia files on the Web.
Web browsers send HTTP requests for web pages and their associated files.
Web servers send HTTP responses back to the web browsers.
Jozef Goetz, 2015
54TCP/IP - Transmission Control Protocol/Internet Protocol
TCP/IP has been adopted as the official communication protocol of the Internet.
TCP and IP have different
functions that work together to ensure reliable communication over the Internet.
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55TCPTransmission Control Protocol
Purpose is to ensure the integrity of communication
Breaks files and messages into individual units called packets
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56
OSI and TCP/IP model
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57IP - Internet Protocol
A set of rules that controls how data is sent between computers on the Internet.
IP routes a packet to the correct destination address.
Once sent, the packet gets successively forwarded to the next closest router (a hardware device designed to move network traffic) until it reaches its destination.
Jozef Goetz, 2015
58IP Address Each device connected to the Internet has a
unique numeric IP address.
These addresses consist of a set of four groups of numbers, called octets. 66.94.234.13 will get you Yahoo! Use
ping 66.94.234.13 ping yahoo.com or ping google.com tracert google.comas exercises
Your IP can be found here http://myip.dk/
exercises
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59IP Address.
The IP address may correspond to a domain name. Divides the Internet into logical groups and
understandable names The Domain Name System (DNS) associates
these IP Addresses with the text-based URLs and domain names you type into a web browser. Browser: http://google.com DNS: 64.233.187.99
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A C (client) and a S (server) communicate with each other using addresses.
e.g. An e-mail address may look like [email protected] Apps program uses an alias name instead of an IP address So the alias address is mapped to the IP address by DNS
(Domain Name System) services
Client-server model
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scheme://host.domain:port/path/filename scheme - defines the type of Internet service. The most common type is http
host - defines the domain host (the default host for http is www) and domain - defines the Internet domain name, like w3schools.com
port - defines the port number at the host (the default port number for http is 80) path - defines a path at the server (If omitted, the document must be stored at the root directory of the web site) filename - defines the name of a document/resource
The protocol is the client/server program used to retrieve the document. Many different protocols can retrieve a document; among them are FTP or HTTP The most common today is HTTP
The host ( = Web server name + domain name) is the computer on which the information is located, although the name of the computer can be an alias. Ex. www.students.laverne.edu, where “laverne.edu” is a domain name, students – computer name Web pages are usually stored in computers, and computers are given alias names that usually begin with
the characters "www", so www.students - alias This is not mandatory, however, as the host can be any name given to the computer that hosts the Web
page. The URL can optionally contain the port number of the server.
If the port is included it is inserted between the host and the path, and it is separated from the host by a colon.
Path is the pathname of the file where the information is located. Note that the path can itself contain slashes that, separate the directories from the subdirectories and files.
URL
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62URL - Uniform Resource Locator
URL Represents the
address of a resource A Web page A graphic file A Java applet
on the Internet.
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63Domain Name
Domain Name - locates an organization or other entity on the Internet
The Domain Name System (DNS) Divides the Internet into logical groups and
understandable names by identifying the exact address and type of the organization.
Associates the text-based domain names with the unique numeric IP Address assigned to a device.
Browser: http://google.com DNS: 64.233.187.99
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Domain Name System
64
The Domain Name System (DNS) associates Domain Names with IP addresses.
64
Domain Name
IP Address
Use TCP/IP to send HTTP Request
Web Server
Use TCP/IP to send HTTP Responseswith web page files & images
Web Browser
Web Browserdisplays web page
DNS
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65 Example of using the DNS service
The DNS client program sends a request to a DNS server to map the e-mail address to the corresponding IP address. However, people prefer to use names instead of numeric addresses. Therefore, we need a system that can map a name to an address or an
address to a name.
ipconfig /all - to see DNS address at your computer (exercise)
DNS server
Jozef Goetz, 2015
66Domain Name System The Domain Name System (DNS) associates
Domain Names with IP addresses.
Each time a new URL is typed into a web browser:1.The DNS is accessed
2.The corresponding IP address is obtained and returned to the web Browser
3.The web browser sends an HTTP request to the destination computer with the corresponding IP address
4. The web server receives the HTTP request 5.The necessary files are located and sent by HTTP responses to
the web browser6.The web browser renders and displays the web page and
associated files
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67
Generic domains The generic
domain defines registered hosts according to their generic behavior.
Each node defines a domain, which is an index to the domain name space database.
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68TLD - Top-Level Domain Namee.g. www.yahoo.com A top-level domain (TLD)
identifies the right-most part of the domain name.
Current generic TLDs:.com, .org, .net, .mil, .gov, .edu, .int, .aero, .name, .biz, .museum, .info, .coop, .pro
A second-level domain (TLD) e.g. yahoo.com – domain name
www – the name of the Web server
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Generic domain labels
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Country domains
The country domains section uses two-character country abbreviations (e.g., us for United States).
Examples: .tv, .ws, .au, .jp, .uk See http://www.iana.org/cctld/cctld-
whois.htm for a complete list.
Second labels can be organizational, or they can be more specific, national designations. The United States, e.g., uses state
abbreviations as a subdivision of us (e.g., ca.us.).
The address anza.cup.ca.us can be translated to De Anza College in Cupertino, California, in the United States.
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Domain names and labels
Label: Each node in the tree has a label,
which is a string with a maximum of 63 characters.
The root label is a null string (empty string).
Domain Name: Each node in the tree has a domain
name. A full domain name is a
sequence of labels separated by dots (.).
The domain names are always read from the node up to the root.
The last label is the label of the root (null) which means the last character is a dot
because the null string is nothing.
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Dotted-decimal notation and binary notation for an IPv4 addressbase on 32 bit IP address
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73Next Generation Internet
The current Internet was built to hold about 4 billion unique IP addresses. But because every fax machine, cell phone, computer, Blackberry, and dozens of
other gadgets that require Internet access need their own unique IP address, the current Internet has become overloaded.
These network devices have now eaten away more than 90% of the Internet’s remaining IP address pool
The IP address of IPv6 is 128 bits and it covers the # of hosts 6 x 2^28 times the present world population is 100-times faster than the current Internet
Now you can see why Forbes calls The Next Generation Internet a “$10 trillion industry over the next decade.”
The federal government publication, Government Security says that, “this conversion to IPv6 will revolutionize the capabilities of Internet networks by enabling literally billions of trillions of new devices to communicate information online.”
the U.S. government issued a mandate requiring all 1,175 federal agencies, government contractors, service providers, and vendors in America to upgrade their network equipment – routers, computer servers, switches
Nokia has developed a prototype handset that supports the Next Generation Internet and will revolutionize the quality of voice over IP, streaming video, and other applications delivered to wireless devices
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Today, there are many registrars; their names and addresses can be found at
http://www.intenic.net
To register, the organization needs to give the name of its server and the IP address of the
server.
e.g. a new commercial organization named wonderful with a server named ws and IP address 200.200.200.5 needs to give: to registrars:
– Domain name: ws.wonderful.com– IP adr: 200.200.200.5
REGISTRARSREGISTRARS
Jozef Goetz, 2015
75Markup Languages SGML – Standard Generalized Markup
Language A standard for specifying a markup language or tag
set
HTML – Hypertext Markup Language the set of markup symbols or codes placed in a file
intended for display on a web browser. HTML is a collection of tags that are encased between < and
> a standardized system for tagging text files to achieve font,
color, graphic, and hyperlink effects on World Wide Web pages.
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76Markup Languages
HTML (Hypertext Markup Language) limitations Lack of extensibility
Inability to add or change features– Developers become frustrated– Code becomes erroneous
Led to more development on HTML W3C created Cascading Style Sheets (CSS) as temporary
solution– New technology for formatting documents
Led to research for a standardized extensible language– W3C developed Extensible Markup Language (XML)
• Combined power of Standard Generalized Markup Language (SGML) with simplicity of HTML
• Developed XML-based standards for style-sheets and advanced hyperlinking
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77Extensible Markup Language (XML)
Become the universal technology for data representation
XML – eXtensible Markup Langauge A text-based language designed to describe, deliver, and
exchange structured information. It is not intended to replace HTML it is intended to extend the power of HTML by separating
data from presentation. – Because an XML document describes data in ASCII
any application can process XML documents
• Improves Web functionality and interoperability• XML documents can be easy manipulated by any
app that can process text so it reduces server load and network traffic
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78Extensible Markup Language (XML)
Here's an example of the above data in XML:<Customers> <Customer> <LastName>JONES</LastName> <FirstName>JOHN</FirstName> <Telephone>5555551212</Telephone> <Address>9902 BROADWAY</Address> <City>NEW YORK</City> <State>NY</State> <Zip>10010</Zip> </Customer> <Customer> <LastName>SMITH</LastName> <FirstName>MABEL</FirstName> <Telephone>5555559999</Telephone> <Address>674 ANYSTREET</Address> <City>CHICAGO</City> <State>IL</State> <Zip>60614</Zip> </Customer> </Customers>
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79Markup Languages (2) XML
Integration with applications not only via Web services– Communication between applications employ XML– Structure allows easy integration with database
applications
XHTML – eXtensible Hypertext Markup Language Developed by the W3C as the reformulation of HTML 4.01
as an application of XML. It combines the formatting strengths of HTML 4.01 and the
data structure and extensibility strengths of XML. +’s: adds new tags and interoperability with mobile devices
XHTML is essentially HTML in an XML format
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80Markup Languages (3) The relationship between
XHTML, HTML, and XML HTML is a subset of SGML. XML is a highly functional subset of SGML. XHTML extends and subsets HTML. XHTML uses the syntax of XML
XHTML
HTML 4.0 XMLSyntax
HTML 5:
The next version of HTML 4 and XHTML 1
http://www.w3.org/html/
SGML
Jozef Goetz, 2015
The Relationship between HTML5 and XHTML
HTML5 is not really a rejection of XHTML; it has some of the best features of both HTML 4 and XHTML: Simple doctype: The doctype definition (the boilerplate code that begins every web page) for XHTML was
really complicated. Even people who taught classes and wrote books about it never memorized the doctype, but had to copy and paste it every time. HTML5
has a very simple and clean document definition, and it's once again possible to write a page from memory.
Separation of content and style: HTML5 does not include the style tags from HTML 4 (font, center, and so on), instead requiring developers to use CSS for all styling. Likewise, frames and table-based layout are discouraged in favor of CSS-style layout.
Validation support: Validation turned out to be a very useful tool, so HTML5 can be validated just like XHTML.
The W3C validator currently supports HTML5, and other validation tools are coming online. Validation is an easy way to eliminate goofy coding mistakes and can greatly simplify your coding after you start adding programming support to your documents.
Strict tradition: The coding standards of HTML5 are more like XHTML than HTML 4. Although it's still possible to use sloppy coding in HTML5, most developers use the XHTML strict standards to make the code easier to read and more predictable.
Tighter integration of CSS and programming languages: Perhaps the most important feature of HTML5 is its humility. While HTML is still the central language of the Internet, HTML5 is really about distributing control to other languages. HTML5 is designed as a
central glue that ties together many other technologies: CSS for visual layout, JavaScript for client-side programming, server-side languages like PHP for server control, and databases.
New capabilities: Many of the new features of HTML5 are not technically HTML but advances in the various other related technologies (integrated databases, new JavaScript syntax, new CSS features, and so on).
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82Checkpoint 1.2
1. Describe the components of the client/server model as applied to the Internet.
2. Identify two protocols used on the Internet to convey information that use the Internet but do not use the Web.
3. Explain the similarities and differences between a URL and a domain name.
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83Future Internet & Web Trends Continued importance of E-Commerce Wireless Web access Need for skilled technical workers IPV6 Mobile Access
will overtake PCs as the most common Web access device worldwide
Blogs blog is short for weblog. A weblog is a journal (or newsletter) that is frequently updated and intended for general public consumption. Blogs generally represent the personality of the author or the Web site.
Podcasts are audio, video file on the Web they may take the format of an audio blog, radio show, or interview
RSS (Really Simple Syndication, or Rich Site Summary) Typically delivered by an RSS feed (a summary of new items posted to the website or blogs) A newsreader is needed to access the info. Some browsers can display RSS feeds. The newsreader polls the feed URL at intervals and displays the new headlines. RSS provides web developers with a method to push new content to interested parties and hopefully generate
return visits to the site
Web 2.0 and AJAX – dynamic websites and social network websites Wikis
Are form of a social software in action – visitors sharing their collective knowledge to create freely used by all. The most powerful wiki is Wikipedia (wikipedia.org), an on line encyclopedia.
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84Summary
This chapter provided a brief overview of Internet, Web, and introductory networking
concepts.