1. P.Miller@ukoln.ac.uk http://www.ukoln.ac.uk/
XML and RDF
Paul Miller
Interoperability Focus
UK Office for Library & Information Networking (UKOLN)
UKOLN is funded by Resource: the Council for Museums, Archives and Libraries, the Joint Information Systems Committee (JISC) of the Further and Higher Education Funding Councils, as well as by project funding from JISC and the EU. UKOLN 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Technically superseded by XHTML now….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

3. © Cabinet Office, Crown Copyright Reserved

4. © Cabinet Office, Crown Copyright Reserved

5. HTML Features Easy to create Permissive Occasionally ambiguous
MS Word, etc.
Permissive
<p> <UL> <li>Blah… </p>
</ul>
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

7. DRAFT

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 XHTML 1.1 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

10. © CCTA, Crown Copyright Reserved

11. © CCTA, Crown Copyright Reserved

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

13. XHTML Features Tags and values are case sensitive
<P>Blah… </P>
<P>Blah… </p>
<p>Blah… </p>
All different. Only one is correct.

14. û ü XHTML Features All tags must nest
<p>here is a paragraph containing <em>emphasis.</p></em>
<p>here is a paragraph containing <em>emphasis.</em></p> û ü

15. û ü XHTML Features All tags must close <p>here is a paragraph.
<p>here is a paragraph.</p> û ü

16. û ü XHTML Features Attribute values must be quoted
<img src=image.gif alt=Some explanatory text>
<img src=“image.gif” alt=“Some explanatory text” /> û ü

17. û ü ü XHTML Features Empty elements must close, too <br>
<br></br>
<br /> û ü ü

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

20. What is RDF? Founded upon ‘triples’ e.g. 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
Resource
Property
Value
Statement

22. RDF model
Resource
Creator
“Paul Miller”