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An XML Introduction
Next Generation Web Data
Ian GRAHAMCentre for Academic TechnologyTel: 978-4548Email: <ian.graham@utoronto.ca>Talk: http://www.utoronto.ca/ian/talks/
Overview
An XML example -- so what’s so special about XML?
The birth of the Web -- HTMLHTML is not enough -- why?XML for universal dataCommon uses and applications
XML Example: test.xml
<?xml version="1.0" encoding="iso-8859-1” ?><html xmlns="http://www.w3.org/TR/xhtml1" ><head> <title> Title of text XHTML Document </title></head><body><div class="myDiv"> <h1> Heading of Page </h1> <p> here is a paragraph of text. I will include inside this paragraph a bunch of wonky text so that it looks fancy. </p> <p>Here is another paragraph with <em>inline emphasized</em> text, and <b> absolutely no</b> sense of humor. </p> <p>And here is another paragraph, this one containing an <img
src="image.gif" alt="waste of time" /> inline image, and a <br /> line break. </p></div> </body></html>
It Looks Like HTML ….
Sort of ….Tags look just like HTML tags
(although XML lets you ‘create’ your own)
The “red bits” are special XML stuff (we will discuss them later)
It’s got .xml at the end
The Birth of the Web
The HyperText Markup Language A simple language for distributing text
All that other stuff URLs, HTTP, CGI ...
HTML Evolution
Started with very few tags …Language evolved, as more tags
were added forms tables fonts frames
HTML Problems
Desire for personalized tags
Want to put data into HTML form mathematics, database entries, literary
text, poems, purchase orders ….
HTML just isn’t designed for that!
HTML Problems (2)
Software processing Server
management of data
But -- HTML is so ill-formed, this is hard!
HTML
HTML
HTML
HTML
HTML
Idea: Back to the Basics
HTML was defined using SGML Standard Generalized Markup Language A meta-language for defining languages.
Complex, sophisticated, powerful
Idea: Use SGML
Languages based on SGML
SGML
HTML TEI DocBook
. . .
Problems with SGML
Too complicated a languageRules are too strict
Can’t distribute ‘loosely’ formatted text (like HTML)
Not good in a distributed environment
Can’t mix different data together Can’t add arbitrary tags
Idea (2): “Webified” SGML
New eXtensible Markup Language: XML
Can use XML to define new languagesDistributes easily on the WebCan mix different types of data
together can easily add new tags, and tell a
browser what to do with them.
Basic XML Rules
Tags like in HTML, but ...
Technical details Tag names are case-sensitive Always need end tags Special empty-element tags Always quote attribute values
Like this example …..
<?xml version="1.0" encoding="iso-8859-1"?><html xmlns="http://www.w3.org/TR/xhtml1" ><head> <title> Title of text XHTML Document </title></head><body><div class="myDiv"> <h1> Heading of Page </h1> ….. <p>And here is another paragraph, this one containing an <img src="image.gif" alt="waste of time" /> inline image, and a <br /> line break. </p></div> </body></html>
XML Things
<?xml version=“1.0” encoding=“iso-8859-1” ?> Says that this is an XML document
<html xmlns=“http://www.w3.org/TR/xhtml1”> Says that the meaning of the tags inside (and
including) the html “element” are defined here.
Evolution of XML
Many XML languages, optimised for different roles
MathML -- for mathematics SMIL -- for synchronised multimedia RDF -- for describing “things” XUL -- for describing the Navigator 5
user interface
MathML
Designed to express semantics of maths
Also can express layout
Cut & paste into Maple, Mathematica
x2 + 4x + 4 =0<mrow> <mrow> <msup> <mi>x</mi> <mn>2</mn>
</msup> <mo>+</mo> <mrow> <mn>4</mn> <mo>&invisibletimes;</mo> <mi>x</mi> </mrow> <mo>+</mo> <mn>4</mn> </mrow> <mo>=</mo> <mn>0</mn></mrow>
SMIL
Synchronised Multimedia Integration Language
Integration of multimedia with text, audio, video
Support in RealPlayer G2
SMIL Example<smil> <head> <meta name="title" content="Online Teaching Services promo" /> <meta name="author" content="Jay Moonah, CAT" /> <layout type="text/smil-basic-layout"> <root-layout width="280" height="316" background-color="white"/> <region id="AnimChannel1" title="AnimChannel1" left="0" top="0" height="265" width="280" fit="hidden"/> </layout></head><body> <par title="Online Teaching Services promo" author="Jay Moonah, CAT" > <audio src="final.rm" id="Soundtrack" title="Soundtrack"/> <animation src="otscompfin.swf" id="Animation" region="AnimChannel1" title="Animation" fill="freeze"/> <text src="cc.rt" id="caption" region="cc" title="cc" fill="freeze"/> </par></body></smil>
XHTML: NextGen HTML<?xml version="1.0" encoding="iso-8859-1"?><html xmlns="http://www.w3.org/TR/xhtml1" ><head> <title> Title of text XHTML Document </title></head><body><div class="myDiv"> <h1> Heading of Page </h1> <p> here is a paragraph of text. I will include inside this paragraph a bunch of wonky text so that it looks fancy. </p> <p>Here is another paragraph with <em>inline emphasized</em> text, and <b> absolutely no</b> sense of humor. </p> <p>And another paragraph, this one with an <img src="image.gif" alt="waste of time" /> image, and a <br /> line break. </p></div> </body></html>
XHTML
Just like HTML, but based on XML rules
Will support integration of different data into a single document
XHTML and other Data
<?xml version="1.0" encoding="iso-8859-1"?><html xmlns="http://www.w3.org/TR/xhtml1" ><head> <title> Title of XHTML Document </title></head><body><div class="myDiv"> <h1> Heading of Page </h1> <mathml xmlns=“http://www.w3.org/TR/mathml”> … MathML markup … </mathml> <p> more html stuff goes here </p> <smil xmlns=“http://www.w3.org/TR/smil1”> … SMIL markup … </smil></div> </body></html>
Displaying XML
More complicated than HTML XML represents data only, not how it
looks Need extra instructions (a “style
sheet” document) to define how things should look
What Browsers Do Now?
Netscape 5 -- ignores the tags ... or so it seems ...
Internet Explorer 5 -- shows a tree of elements
Navigator 4, Internet Explorer 4Uggh…… (can’t handle it)
Other Use: Data Abstraction
XML as a universal format for data interchange
Machines exchange data as XML-format messages
Eliminates proprietary data formats Lots of XML processing software
available
XML Messaging
FactorySupplier
Supplier
Supplier
Place order
Response
XML Messaging
DatabaseOther DB
Other DB
Other DB
Request/send data
Request/send data
Example Message
<partorders xmlns=“http://myco.org/Spec/partorders.desc”> <order ref=“x23-2112-2342” date=“25aug1999-12:34:23h”> <desc> Gold sprockel grommets, with matching
hamster</desc> <part number=“23-23221-a12” /> <quantity units=“gross”> 12 </quantity> <delivery-date date=“27aug1999-12:00h”> </order> <order ref=“x23-2112-2342” date=“25aug1999-12:34:23h”> …. Order something else ….. </order></partorders>
The XML Family Tree
SGML
XML
HTML TEI
. . .
. . .
XHTML
SMIL
MathML
SpeechML
RDF
XUL
Other Examples
XUL: XML User Interface Language How Navigator 5 configures its interface
RDF: Resource Description Framework For describing things Used by Netscape Open Catalog project
to define Web accessible resources
Summary
a framework for distributing data on the Web
an integration tool for mixing different types of data
a universal format for exchanging data between machines
An XML Introduction
Next Generation Web Data
Ian GRAHAMCentre for Academic TechnologyTel: 978-4548Email: <ian.graham@utoronto.ca>Talk: http://www.utoronto.ca/ian/talks/
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