1 XML and RDF Paul Miller Interoperability Focus UK Office for Library & Information Networking (U KOLN ) U KOLN is funded by Resource: the Council for Museums, Archives and Libraries, the Joint Information Systems Committee (J ISC ) of the Further and Higher Education Funding Councils, as well as by project funding from J ISC and the EU. U KOLN also receives support from the Universities of Bath and Hull where staff are based.

2 What is HTML ? HyperText Markup Language World Wide Web Consortium recommendation (currently at version 4.01) Simplified subset of SGML for use on Web Widely deployed and understood Difficult to extend Supported by major vendors, mostly Technically superseded by XHTML now…. See

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5 HTML Features Easy to create MS Word, etc. Permissive Blah… Occasionally ambiguous Case Insensitive.

6 What is XML ? eXtensible Markup Language World Wide Web Consortium recommendation Simplified subset of SGML for use on Web Addresses HTML’s lack of evolvability Easily extended Supported by major vendors Increasingly used as a transfer syntax, but capable of far more…. See

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8 XML Features Extensible Stricter than HTML on some rules Therefore less ambiguous Case Sensitive Notions of ‘well–formed’ and ‘valid’ A well formed document obeys the rules of XML A valid document further obeys the constraints of an associated DTD or equivalent.

9 What is XHTML ? XHTML 1.0 An expression of HTML 4.01 in XML The current W3C recommendation for creating web documents XHTML 1.1 A strict expression of HTML 4.01 in XML –Layout tagging removed altogether –Constructed in a modular fashion Currently a W3C proposal. See

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12 XHTML Features …which apply to other applications of XML, such as RDF…

13 XHTML Features Tags and values are case sensitive Blah… All different. Only one is correct.

14 XHTML Features All tags must nest here is a paragraph containing emphasis. 

15 XHTML Features All tags must close here is a paragraph. 

16 XHTML Features Attribute values must be quoted 

17 XHTML Features Empty elements must close, too 

18 Beyond XML “…XML allows users to add arbitrary structure to their documents but says nothing about what the structures mean.” See berners-lee.html

19 World Wide Web Consortium Recommendation Fully compliant application of XML Improves upon XML, HTML, PICS… Machine understandable metadata! Supports structure Increasing interest. See What is RDF?

20 What is RDF? Founded upon ‘triples’ A resource has properties Each property has a value e.g. This presentation has a creator The creator is “Paul Miller” This presentation has a title The title is “XML and RDF”.

21 RDF model Resource Property Value Resource Statement

22 RDF model Resource Creator “Paul Miller”