1. Semantic Web in Depth RDFa, GRDDL and POWDER Dr Nicholas Gibbins - nmg@ecs.soton.ac.uk 2013-2014

2. Embedding Semantic Web Data http://www.flickr.com/photos/40472757@N07/4508416502/

3. Embedded Data Publishing patterns for linked data that we’ve already considered make the assumption that we’re publishing directly in RDF/OWL What if the data already exists in a web resource, in some form?

4. Embedded Data Republishing the data separately introduces redundancy, and the possibility of inconsistency - embed our SW data in the web resource Two main approaches: –GRDDL –RDFa

5. GRDDL

6. Given a document in some XML format, how can we extract the relevant portions and make them available to SW agents? GRDDL (Gleaning Resource Descriptions from Dialects of Languages) uses XSLT stylesheets to transform documents XML doc XML doc XSLT style sheet GRDDL Processor RDF/ XML

7. Using GRDDL with XML In well-formed XML, link to XSLT transformation using grddl:transformation attribute –Need to introduce grddl: namespace Are You Experienced? [...]

8. Using GRDDL with XHTML Link to XSLT transformation using link element –Introduce GRDDL in profile Some Document [...] [...]

9. RDFa

10. Yet another syntax for RDF… –Designed for embedding structured data in web pages –Stored structure in attributes (the ‘a’ in ‘RDFa’)

11. RDFa Example Jo's Friends and Family Blog I'm holding one last summer Barbecue, on September 16th at 4pm. Jo Smith. Web hacker at Example, Inc. You can contact me via email.

12. Setting namespaces Jo's Friends and Family Blog I'm holding one last summer barbecue, on September 16th at 4pm. Jo Smith. Web hacker at Example, Inc. You can contact me via email.

13. Showing an instance of a class Class membership is indicated using the typeof attribute: I'm holding one last summer barbecue, on September 16th at 4pm.

14. Showing an instance of a class Class membership is indicated using the typeof attribute: I'm holding one last summer barbecue, on September 16th at 4pm. _:a rdf:type cal:Event.

15. Using properties: predicates The predicate of a triple is indicated using the property attribute: I'm holding one last summer barbecue, on September 16th at 4pm.

16. Using properties: predicates The predicate of a triple is indicated using the property attribute: I'm holding one last summer barbecue, on September 16th at 4pm.

17. Using properties: literal objects The object of a literal-valued triple is given by the content of the element bearing the property attribute I'm holding one last summer barbecue, on September 16th at 4pm. _:a cal:summary “one last summer barbecue”.

18. Using properties: substitute values The content of an element may be substituted for using the content attribute: I'm holding one last summer barbecue, on September 16th at 4pm. _:a cal:start “2007-09-16T16:00:00”.

19. Using properties: datatypes The datatype of a literal-value object is indicated using the datatype attribute: I'm holding one last summer barbecue, on September 16th at 4pm. _:a cal:start “2007-09-16T16:00:00”^^xsd:dateTime.

20. Using properties: resource objects The object of a resource-valued triple is given by the content of the resource attribute: Jo Smith. Web hacker at Example, Inc. You can contact me via email. _:b foaf:workplaceHomepage.

21. Identity The subject of a triple is indicated using the about attribute: Jo Smith. Web hacker at Example, Inc. You can contact me via email. _:b foaf:workplaceHomepage.

22. Identity The subject of a triple is indicated using the about attribute: Jo Smith. Web hacker at Example, Inc. You can contact me via email. foaf:workplaceHomepage.

23. Using existing links Existing links may be used to construct triples with resource- valued objects: Jo Smith. Web hacker at Example, Inc. You can contact me via email.

24. Using existing links The rel attribute is used to indicate the predicate: Jo Smith. Web hacker at Example, Inc. You can contact me via email.

25. Using existing links The href attribute is used to indicate the object: Jo Smith. Web hacker at Example, Inc. You can contact me via email. foaf:mbox.

26. Original File Jo's Friends and Family Blog I'm holding one last summer barbecue, on September 16th at 4pm. Jo Smith. Web hacker at Example, Inc. You can contact me via email.

27. Annotated File Jo's Friends and Family Blog I'm holding one last summer barbecue, on September 16th at 4pm. Jo Smith. Web hacker at Example, Inc. You can contact me via email.

28. Contained Triples _:a rdf:type cal:Event ; cal:summary “one last summer barbecue” ; cal:start “2007-09-16T16:00:00”^^xsd:dateTime. rdf:type foaf:Person ; foaf:name “Jo Smith” ; foaf:workplaceHomepage ; foaf:mbox.

29. POWDER

30. Protocol for Web Description Resources RDF lets us make statements about a single resource at a time –an RDF triple has only one subject! POWDER is an XML format for describing groups of resources Lineage goes back to PICS – Platform for Internet Content Selection

31. W3C Language Other MCF OIL PICS RDF(S) OWL 1996 1999 2004 2001 2000 SHOE DAML RDF(S) Languages of the Semantic Web DAML+OIL OWL 1.1 2002 1998 1997 2003 2005 2006 2007 2009 OWL 2 2008

32. General Syntax //description of entity making the description //description resource //specifier for things being described // descriptions of things being described

33. General Syntax //description of entity making the description //description resource //specifier for things being described // descriptions of things being described

34. General Syntax //description of entity making the description //description resource //specifier for things being described // descriptions of things being described

35. General Syntax //description of entity making the description //description resource //specifier for things being described // descriptions of things being described

36. General Syntax //description of entity making the description //description resource //specifier for things being described // descriptions of things being described

37. Example 2007-12-14T00:00:00 example.com red square Everything on example.com is red and square

38. Further Reading Gleaning Resource Descriptions from Dialects of Languages W3C Recommendation 11 September 2007 http://www.w3.org/TR/grddl/ RDFa Core 1.1 W3C Recommendation 22 August 2013 http://www.w3.org/TR/rdfa-syntax/ RDFa 1.1 Primer (essential reading!) W3C Working Group Note 22 August 2013 http://www.w3.org/TR/xhtml-rdfa-primer/ POWDER Primer W3C Working Group Note 1 September 2009 http://www.w3.org/TR/powder-primer/