XML, HTML and All That What do they Mean, and Why Should you Care? Ian GRAHAM Centre for Academic Technology Tel: Talk:

Overview zA little Web history and the birth of HTML zHTML is not enough -- why? zXML for universal data yFor communicating information of all types zExamples of XML in action zProfound conclusions...

The Birth of the Web zThe HyperText Markup Language yA simple language for distributing text zAll the other parts -- yURLs, HTTP, CGI...

Four Main Components zURLs: For addressing things zHTTP: For transporting data zCGI: For adding functionality zHTML: For encoding text information

HTML HTTP Shoutcast NNTP FTP URLs CGI Databases & other software

HTML zA simple, general-purpose language zSimple hypermedia zOriginal idea -- yCollaborative authoring yMerging of concept of authoring/viewing

HTML Evolution zStarted with very few tags … zsimple requirements (only need to no a little bit about the tags, and then just muddle through) zLanguage evolved, as more tags were added yforms, images, tables, frames, fonts,...

HTML Problems (1) zEveryone wanted personalized tags zWant to put other data into HTML ymathematics, database entries, literary text, poems, purchase orders …. zHTML just isn’t designed for that!

HTML Problems (2) zSoftware processing yServer management of data zBut -- HTML is so ill- formed, this is hard! HTML Web server engine

HTML Problems (3) zSoftware processing yClient data processing (machine--machine communication) zBut -- HTML is so ill- formed, this is hard! HTML Client software Database, viewer, whatever.... (from somewhere on the Web...)

Idea: Back to Basics zHTML was defined using SGML yStandard Generalized Markup Language yA meta-language for defining languages zComplex, sophisticated, powerful zIdea: Use SGML

Languages based on SGML SGML HTMLTEIDocBook...

Problems with SGML zSGML Too complicated zRules too strict yCan’t distribute ‘loosely’ formatted text (like HTML) zNot good in a distributed environment zCan’t mix different data together yCan’t add arbitrary tags

Idea (2): “Webified” SGML zNew eXtensible Markup Language: XML zCan use XML to define new languages zDistributes easily on the Web zCan mix different types of data together ycan easily add new tags, and tell a browser what to do with them (more or less....)

Basic XML Rules zTags written as with HTML, but... zTechnical details yTag names are case-sensitive yAlways need end tags ySpecial empty-element tags yAlways quote attribute values

Like this example ….. Title of text XHTML Document Heading of Page ….. And here is another paragraph, this one containing an inline image, and a line break. XML stuff

Special XML Things z ySays that this is an XML document z ySays that the meaning of the tags inside (and including) the html element are defined as belonging in the same “space” of names. xmlns  XML namespace

Evolution of XML zMany XML languages, optimised for different Web roles yMathML -- for mathematics ySMIL -- for synchronised multimedia yRDF -- for describing “things” yXUL -- for describing the Nav5 user interface ySpeechML -- for synthesised voices

MathML zDesigned to express layout of maths zAlso can express semantics zCut & paste into Maple, Mathematica z x 2 + 4x + 4 =0 x &invisibletimes; x + 4 = 0

SMIL zSynchronised Multimedia Integration Language zIntegration of multimedia with text, audio, video zSupport in RealPlayer G2

SMIL Example <region id="AnimChannel1" title="AnimChannel1" left="0" top="0" height="265" width="280" fit="hidden"/> <animation src="otscompfin.swf" id="Animation" region="AnimChannel1" title="Animation" fill="freeze"/>

XHTML: NextGen HTML Title of text XHTML Document Heading of Page here is a paragraph of text. I will include inside this paragraph a bunch of wonky text so that it looks fancy. Here is another paragraph with inline emphasized text, and absolutely no sense of humor. And another paragraph, this one with an <img src="image.gif" alt="waste of time" /> image, and a line break.

XHTML zJust like HTML, but based on XML rules zWill support integration of different data into a single document y(Doesn’t work that way now, unfortunately)

XHTML and other Data Title of XHTML Document Heading of Page … MathML markup … more html stuff goes here … SMIL markup …

Displaying XML zMore complicated than HTML yXML represents data only, not how it looks yNeed extra instructions (a “style sheet” document) to define how things should look

What Browsers Do Now? zNavigator 4, Internet Explorer 4 yUggh…… (can’t handle XML at all) zInternet Explorer 5 -- shows a tree of elements zNetscape 5 -- ignores the tags... or so it seems...

Other Use: Data Abstraction zXML as a universal format for data interchange yMachines exchange data as XML-format messages yEliminates proprietary data formats yLots of XML processing software available

XML Messaging: Business Factory Supplier Place order Response

XML Messaging: Database Database Other DB Request/send data

Example Message Gold sprockel grommets, with matching hamster 12 …. Order something else …..

Other Examples zXUL: XML User Interface Language yHow Navigator 5 configures its interface yDefines structure and software integration ( zRDF: Resource Description Framework yFor describing things yUsed by Netscape Open Catalog project to define Web accessible resources (

The XML Family Tree SGML XML HTMLTEI XHTML SMIL MathML SpeechML RDF XUL

XML Summary zan integration tool for mixing different types of data za universal format for exchanging data between machines za framework for distributing information on the Web

XML, HTML and All That Ian GRAHAM Centre for Academic Technology Tel: Talk: