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

Overview zThe birth of HTML zWhy HTML was not enough zXML for data encoding zExamples of XML zSome thoughts for the future

HTML zSimple, general-purpose markup language zSimple hypermedia zOriginal idea -- ySupport collaborative authoring yMerge document authoring/viewing

HTML Evolution zStarted with very few tags … zSimple requirements yonly need to know a little bit about the tags, and then just “muddle through”) zEvolved to have more tags were added yforms, images, tables yframes, fonts, applets, embeds....

Outline zThe birth of HTML zWhy HTML was not enough zXML for data encoding zExamples of XML zSome thoughts for the future

HTML Problems (1/3) zPeople wanted additional tags yformatting other types of data zDesire for other types of data ymathematics, database entries, literary text, ‘messages’ (e.g., a purchase order) …. zDifficult/impossible with HTML yCan’t arbitrarily extend the language

HTML Problems (2/3) zSoftware processing yServer management of data zBut -- HTML is so ill- formed, this is hard! HTML Web server engine

HTML Problems (3/3) zSoftware processing yClient data processing (machine -- machine communication) zAgain, hard because - - HTML is generally so ill-formed. HTML Data processor Database, viewer, whatever.... (from somewhere on the Web...)

Three New “Patterns” zDistribution of stuff to read or see (like HTML, but more so) zModeling data inside a Web application (like a text database) zStructure of data messages sent between machines.... HTML is ok, at best, for the first....

Outline zThe birth of HTML zWhy HTML was not enough zXML for data encoding zExamples of XML zSome thoughts for the future

First Idea: Back to Basics zSince HTML is defined using SGML... yStandard Generalized Markup Language yA meta-language for defining languages yComplex, sophisticated, powerful z... Use SGML instead

Didn’t fly because... zSGML too complicated zSGML rules too strict yNo ‘loosely’ formatted data (like HTML) yNot good in a distributed environment yCan’t mix different data together xCan’t add arbitrary tags

Idea 2 -- XML: The eXtensible Markup Language zA simpler language based on SGML 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 Tag Syntax: zTags written as with HTML, but... zTechnical details yCase-sensitive names yAlways need end tags ySpecial empty-element yAlways quote attribute values....

XML 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 belong in the same “space” of names. xmlns  XML namespace

Outline zWeb history and the birth of HTML zWhy HTML was not enough zXML model for data encoding zExamples of XML zSome thoughts for the future

Evolution of XML zMany XML languages for different roles yMathML -- for mathematics ySMIL -- for synchronised multimedia yXHTML -- XML-ized HTML yRDF -- for describing “things” yHEML -- Historical events, y.... and many others.

MathML: Mathematics 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...

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 with XML syntax zXML model, however, supports integration of different data / languages inside a single XML document:

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 only represents a data structure, not how it looks yNeed extra instructions (a “style sheet” document) to define how things should look ySee example pages on associated Web site.

HTML Processor XML Processor Default rules for HTML markup and formatting Data input HTML XML Rendered / displayed content CSS style sheet(s) No default markup/ formatting rules CSS and/or XSL style sheet(s) + + Namespace- declared processors and rules +

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

Resource/Rich Site Summary zTool for distributing news headlines zUsed by many news services, including: yNetscape Webcenter yMeerkat ( ) ySlashdot ( yMoreover ( RSS --

Actualités Netscape Actualité Netscape - À la une fr Netscape Netcenter RSS Example

Generic XML Messages: Factory/DB Supplier/DB Place order  request/send data Response

Outline zThe birth of HTML zWhy HTML was not enough zXML for data encoding zExamples of XML zSome thoughts for the future

Future Trends zXML for modeling information about things, or resources zDistributed models for managing, linking, and sharing XML information z“Cooperative information Webs” also called.... “The Semantic Web”

Example: HEML zHistorical Event Markup and Linking yA standard, flexible and extensible means of encoding an historical event or series of events in electronic form zLets you create Webs of historical data, cross-related using HEML markup.

Example HEML Record Attack on Gallipoli Gallipoli Peninsula

Example: Data Syndication zA generic mechanism for exchanging “chunks” of information zLets sites / databases / research projects exchange many different types of data zCan contain HEML, RSS, and other data in the same message zhttp://

info about the aggregator metadata about the item the data itself -- this could be HEML, RSS, or whatever additional items in the message Syndication Example

Request new HEML stuff, plus popular news (RSS) and seminar listings (XSeL) containing HTML, RSS, and other data chunks Example Application:

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..... Ian GRAHAM Centre for Academic Technology Tel: Talk:

HTML HTTP URLs CGI Databases; other software Web history: 4 components: HTTP, URLs, CGI and HTML Web server

Open Directory Data zRDF: Resource Description Framework yA language for describing things yUsed by Netscape Open Catalog project to define Web accessible resources ( yRDF describes the catalog structure, and also the items entered into the catalog

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