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DC Architecture WG Meeting: Abstract Model Review & Moving Forward

Review the Abstract Model, discuss RDF resource vs literal issue, XML schema problems, metadata terms identifiers, and DC values in RDF. Major model changes and remaining issues to be addressed.

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DC Architecture WG Meeting: Abstract Model Review & Moving Forward

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  1. DC Architecture WG meeting Wednesday 13.30 - 15.30Seminar Room: 5205 (2nd Floor)

  2. Agenda • Review of the Abstract Model and moving forwardhttp://www.ukoln.ac.uk/metadata/dcmi/abstract-model/ • RDF resource vs. literal issuehttp://www.ukoln.ac.uk/metadata/dcmi/rdf-values/ • XML schema issueshttp://www.ukoln.ac.uk/metadata/dcmi/xmls-issues/ • Identifiers for historical versions of metadata termshttp://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=ind0410&L=dc-architecture&T=0&O=D&P=3366

  3. Review of the year (Sleepy Since Seattle)

  4. …but not that sleepy! • Abstract Model document moved forward (slowly) • “Expressing Dublin Core in HTML/XHTML meta and link elements” issued as a DCMI Recommendation • discussion paper about assigning URIs for metadata terms • something like 200 messages posted to the dc-architecture mailing list

  5. Abstract Model

  6. Major changes • changed 'URI' to 'URI reference' at appropriate points throughout • added 'description set' to the description model to separate out the conceptual grouping of related descriptions (a 'description set') from its instantiation in a particular syntax (a 'record')

  7. Major changes (2) • introduction of 'property/value pair' into the resource model to separate abstract notion of a property from the specific usage of a property to describe a particular resource • modified the definition of 'sub-property' in the resource model

  8. Major changes (3) • added of a note about needing to indicate how 'resource URIs' and 'value URIs' are handled in encoding syntax specifications • explicit indication that 'resource URIs' and 'value URIs' are not supported by the current XML encoding guidelines • explicit indication that 'resource URIs' are not supported by the XHTML encoding syntax

  9. Model summary record (encoded as XHTML, XML or RDF/XML) description set description (about a resource (URI)) vocabulary encoding scheme (URI) statement property (URI) value (URI) representation syntax encodingscheme (URI) value string OR rich value OR related description language(e.g. en-GB)

  10. Remaining issues • possible need for further clarification of how URIs are handled by the AM – in short, dcterms:URI is almost never used and certainly not to indicate a ‘value URI’ • it would be better if we modelled ‘syntax encoding scheme URI’ and ‘vocabulary encoding scheme URI’ as separate entities in the model

  11. Remaining issues (2) • the AM currently restricts the number of ‘parent’ properties that a sub-property can have to a maximum of one - this is an error and will be made unlimited. • does the model get the definitions of ‘simple DC’ and ‘qualified DC’ right? • should the model support ordered lists of values?

  12. RDF resource vs. literal issue

  13. The problem In DC/RDF, these two graphs mean the same thing (in terms of the abstract model) but in RDF they mean different things…

  14. Possible solutions • Status quo • Align behaviour of consuming systems • Align behaviour of consuming and generating systems • Attempt to influence the behaviour of the wider Semantic Web community • Replicate existing DC property semantics in new properties

  15. XML schema issues

  16. Identifiers for historical versions of metadata terms

  17. DC Architecture WG report • agenda: • Abstract Model • encoding DC element values in RDF • XML schema issues • identifiers for DCMI term descriptions • 21 attendees

  18. Wot we did last year… • moved Abstract Model forward slowly • issued XHTML encoding guidelines as a Recommendation • developed issues papers on identifiers • about 200 postings to thedc-architecture mailing list

  19. Abstract Model • discussion around the meanings of ‘simple DC’ and ‘qualified DC’ • no consensus • agreed to remove definitions of these terms from the Abstract Model • discussed possibility of adding support for ‘ordered lists of values’ to the abstract model – little support for this in the room

  20. DC values in RDF • problem: some confusion in RDF implementer community currently • solution (short-term): work item to develop a short clarification document for RDF implementers • solution (long-term): work item to develop a view of possible ‘encoding’ changes to remove confusion and carry out impact analysis • undertaken by small ‘task force’

  21. XML schemas • agreed to provide a persistent URI to the latest version of our XML schemes • agreed to provide two ‘container’ elements for DC descriptions, probably called <dcxml:description> and <dcxml:descriptionSet> • work item: revise DC in XML Guidelines to include explicit mechanism for value URIs

  22. Namespace policy • work item: minimal update to the namespace policy to align some of the terminology with current usage • consider ways of documenting how we assign URIs to DCMI term descriptions

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