An XML Introduction

1
An XML Introduction

• Next Generation Web Data
• Ian GRAHAM
• Centre for Academic Technology
• Tel [phone]
• Email ltian.graham_at_utoronto.cagt
• Talk http//www.utoronto.ca/ian/talks/

2
Overview

• An XML example
• -- so whats so special about XML?
• The birth of the Web -- HTML
• HTML is not enough -- why?
• XML for universal data
• Common uses and applications

3
XML Example test.xml

• lt?xml version"1.0" encoding"iso-8859-1 ?gt
• lthtml xmlns"http//www.w3.org/TR/xhtml1" gt
• ltheadgt
• lttitlegt Title of text XHTML Document lt/titlegt
• lt/headgt
• ltbodygt
• ltdiv class"myDiv"gt
• lth1gt Heading of Page lt/h1gt
• ltpgt here is a paragraph of text. I will
  include inside this paragraph a bunch of
• wonky text so that it looks fancy.
  lt/pgt
• ltpgtHere is another paragraph with
  ltemgtinline emphasizedlt/emgt text, and
• ltbgt absolutely nolt/bgt sense of humor.
  lt/pgt
• ltpgtAnd here is another paragraph, this one
  containing an ltimg src"image.gif"
• alt"waste of time" /gt inline image,
  and a ltbr /gt line break. lt/pgt
• lt/divgt
• lt/bodygtlt/htmlgt

4
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)
• Its got .xml at the end

5
The Birth of the Web

• The HyperText Markup Language
• A simple language for distributing text
• All that other stuff
• URLs, HTTP, CGI ...

6
HTML Evolution

• Started with very few tags
• Language evolved, as more tags were added
• forms
• tables
• fonts
• frames

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HTML Problems

• Desire for personalized tags
• Want to put data into HTML form
• mathematics, database entries, literary text,
  poems, purchase orders .
• HTML just isnt designed for that!

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HTML Problems (2)

• Software processing
• Server management of data
• But -- HTML is so ill-formed, this is hard!

HTML
HTML
HTML
HTML
HTML
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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

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Languages based on SGML
HTML
TEI
DocBook
. . .
SGML
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Problems with SGML

• Too complicated a language
• Rules are too strict
• Cant distribute loosely formatted text (like
  HTML)
• Not good in a distributed environment
• Cant mix different data together
• Cant add arbitrary tags

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Idea (2) Webified SGML

• New eXtensible Markup Language XML
• Can use XML to define new languages
• Distributes easily on the Web
• Can mix different types of data together
• can easily add new tags, and tell a browser what
  to do with them.

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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

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Like this example ..
lt?xml version"1.0" encoding"iso-8859-1"?gt lthtml
xmlns"http//www.w3.org/TR/xhtml1" gt ltheadgt
lttitlegt Title of text XHTML Document
lt/titlegt lt/headgtltbodygt ltdiv class"myDiv"gt
lth1gt Heading of Page lt/h1gt .. ltpgtAnd
here is another paragraph, this one containing
an ltimg src"image.gif" alt"waste
of time" /gt inline image, and a ltbr
/gt line break. lt/pgt lt/divgt lt/bodygtlt/htmlgt
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XML Things

• lt?xml version1.0 encodingiso-8859-1 ?gt
• Says that this is an XML document
• lthtml xmlnshttp//www.w3.org/TR/xhtml1gt
• Says that the meaning of the tags inside (and
  including) the html element are defined here.

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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

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MathML

• Designed to express semantics of maths
• Also can express layout
• Cut paste into Maple, Mathematica

• x2 4x 4 0
• ltmrowgt
• ltmrowgt
• ltmsupgt ltmigtxlt/migt ltmngt2lt/mngt lt/msupgt
  ltmogtlt/mogt
• ltmrowgt
• ltmngt4lt/mngt
• ltmogtinvisibletimeslt/mogt
• ltmigtxlt/migt
• lt/mrowgt
• ltmogtlt/mogt
• ltmngt4lt/mngt
• lt/mrowgt
• ltmogtlt/mogt
• ltmngt0lt/mngt
• lt/mrowgt

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SMIL

• Synchronised Multimedia Integration Language
• Integration of multimedia with text, audio, video
• Support in RealPlayer G2

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SMIL Example
ltsmilgt ltheadgt ltmeta name"title"
content"Online Teaching Services promo" /gt
ltmeta name"author" content"Jay Moonah, CAT" /gt
ltlayout type"text/smil-basic-layout"gt
ltroot-layout width"280" height"316"
background-color"white"/gt ltregion
id"AnimChannel1" title"AnimChannel1"
left"0" top"0" height"265" width"280"
fit"hidden"/gt lt/layoutgt lt/headgt ltbodygt ltpar
title"Online Teaching Services promo"
author"Jay Moonah, CAT" gt ltaudio
src"final.rm" id"Soundtrack"
title"Soundtrack"/gt ltanimation
src"otscompfin.swf" id"Animation"
region"AnimChannel1" title"Animation"
fill"freeze"/gt lttext src"cc.rt"
id"caption" region"cc" title"cc"
fill"freeze"/gt lt/pargt lt/bodygtlt/smilgt
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XHTML NextGen HTML

• lt?xml version"1.0" encoding"iso-8859-1"?gt
• lthtml xmlns"http//www.w3.org/TR/xhtml1" gt
• ltheadgt
• lttitlegt Title of text XHTML Document lt/titlegt
• lt/headgt
• ltbodygt
• ltdiv class"myDiv"gt
• lth1gt Heading of Page lt/h1gt
• ltpgt here is a paragraph of text. I will
  include inside this paragraph
• a bunch of wonky text so that it
  looks fancy. lt/pgt
• ltpgtHere is another paragraph with
  ltemgtinline emphasizedlt/emgt
• text, and ltbgt absolutely nolt/bgt sense
  of humor. lt/pgt
• ltpgtAnd another paragraph, this one with an
  ltimg src"image.gif"
• alt"waste of time" /gt image, and a
  ltbr /gt line break. lt/pgt
• lt/divgt
• lt/bodygtlt/htmlgt

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XHTML

• Just like HTML, but based on XML rules
• Will support integration of different data into a
  single document

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XHTML and other Data

• lt?xml version"1.0" encoding"iso-8859-1"?gt
• lthtml xmlns"http//www.w3.org/TR/xhtml1" gt
• ltheadgt
• lttitlegt Title of XHTML Document lt/titlegt
• lt/headgtltbodygt
• ltdiv class"myDiv"gt
• lth1gt Heading of Page lt/h1gt
• ltmathml xmlnshttp//www.w3.org/TR/mathmlgt
• MathML markup
• lt/mathmlgt
• ltpgt more html stuff goes here lt/pgt
• ltsmil xmlnshttp//www.w3.org/TR/smil1gt
• SMIL markup
• lt/smilgt
• lt/divgt
• lt/bodygtlt/htmlgt

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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

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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 4
• Uggh (cant handle it)

25
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

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XML Messaging
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XML Messaging
Other DB
Request/send data
Database
Other DB
Other DB
Request/send data
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Example Message

• ltpartorders xmlnshttp//myco.org/Spec/partorders
  .descgt
• ltorder refx23-2112-2342 date25aug1999-1234
  23hgt
• ltdescgt Gold sprockel grommets, with
  matching hamsterlt/descgt
• ltpart number23-23221-a12 /gt
• ltquantity unitsgrossgt 12 lt/quantitygt
• ltdelivery-date date27aug1999-1200hgt
• lt/ordergt
• ltorder refx23-2112-2342 date25aug1999-123
  423hgt
• . Order something else ..
• lt/ordergt
• lt/partordersgt

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The XML Family Tree
HTML
TEI
. . .
. . .
XML
SGML
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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

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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

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An XML Introduction

• Next Generation Web Data
• Ian GRAHAM
• Centre for Academic Technology
• Tel [phone]
• Email ltian.graham_at_utoronto.cagt
• Talk http//www.utoronto.ca/ian/talks/