DC Architecture WG meeting Wednesday Seminar Room: 5205 (2nd Floor)

Agenda  Review of the Abstract Model and moving forward  RDF resource vs. literal issue  XML schema issues  Identifiers for historical versions of metadata terms bin/webadmin?A2=ind0410&L=dc- architecture&T=0&O=D&P= bin/webadmin?A2=ind0410&L=dc- architecture&T=0&O=D&P=3366

Review of the year (Sleepy Since Seattle)

…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

Abstract Model

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')

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

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

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

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

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?

RDF resource vs. literal issue

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…

Possible solutions 1. Status quo 2. Align behaviour of consuming systems 3. Align behaviour of consuming and generating systems 4. Attempt to influence the behaviour of the wider Semantic Web community 5. Replicate existing DC property semantics in new properties

XML schema issues

Identifiers for historical versions of metadata terms

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

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 the dc-architecture mailing list

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

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’

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 and  work item: revise DC in XML Guidelines to include explicit mechanism for value URIs

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