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DC Architecture WG meeting

DC Architecture WG meeting. Monday Sept 12 Slot 1: 15.30 - 17.00 Slot 2: 17.30 - 19.00 Location: Seminar Room 4.1.E01. Agenda. review of the year revised "DCMI Namespace Policy" recommendation revising "Guidelines for encoding DC in XML “ recommendation

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DC Architecture WG meeting

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  1. DC Architecture WG meeting Monday Sept 12 Slot 1: 15.30 - 17.00 Slot 2: 17.30 - 19.00 Location: Seminar Room 4.1.E01.

  2. Agenda • review of the year • revised "DCMI Namespace Policy" recommendation • revising "Guidelines for encoding DC in XML“ recommendation • summary of relevant W3C activities (GRDDL and RDF in XHTML) (*) • workplan for next year

  3. Review of the year

  4. Progress during 2005 • DCMI Abstract Model document issued as a Recommendation • agreed persistent URIs for the latest version of our XML schemas • developed draft revised "DCMI Namespace Policy“ • proposed changes to XML guidelines • set up task force to look at DC/RDF issues

  5. Revised DCMI namespace policy

  6. Revised Namespace Policy • new draft policy is available at:http://www.ukoln.ac.uk/metadata/dcmi/namespace-policy/

  7. New terminology • partly to remove confusion with XML namespaces • DCMI namespace - A collection of DCMI term URIs where each term is assigned a URI that starts with the same 'base URI'. The 'base URI' is known as the DCMI namespace URI. (Note that a DCMI namespace is not the same as an 'XML namespace') • DCMI namespace URI - The URI that identifies a DCMI namespace • vocabulary - A collection of terms (often as used in the context of an 'applicationprofile')

  8. Namespaces vs. vocabularies • note that the grouping of term URIs into a DCMI namespace is orthogonal to the grouping of terms into a vocabulary • term URIs are grouped into DCMI namespaces in order to ease the assignment of URIs to terms and to streamline their use in particular encoding syntaxes • terms are grouped into vocabularies in order to meet a functional need

  9. However… • …we quite clearly haven't done this in the case of the DC and DCTERMS namespaces • we have kept two namespaces simply for historical reasons • therefore suggest replicating all the current terms in the DC namespace into the DCTERMS namespace, using RDFS/OWL to explicitly declare equivalences as necessary

  10. XML encoding guidelines

  11. Summary of relevant W3C activities

  12. Summary of DC RDF Taskforce activities

  13. DC RDF Taskforce • Clarification of the recommendations for encoding 'value strings' in DC RDF/XML • Guidelines for encoding DC metadata using the RDF Model • DC Property Domains and Ranges • Proposed changes to DCMI property definitions • DCMI Term Decision Tree

  14. DC RDF Taskforce • Clarification of the recommendations for encoding 'value strings' in DC RDF/XML • Guidelines for encoding DC metadata using the RDF Model • DC Property Domains and Ranges • Proposed changes to DCMI property definitions • DCMI Term Decision Tree

  15. Encoding DC using RDF Model • leading towards new DCMI Recommendation • replacing the current Simple DC in RDF Recommendation and Qualified DC in RDF Proposed Recommendation • mapping from DCMI Abstract Model to RDF Model • therefore can use current and future RDF syntaxs (XML, N3, etc.)

  16. DCMI abstract model • a description is made up of • one or more statements (about one, and only one, resource) and • optionally, the URI of the resource being described (resource URI ) • each statement is made up of • a property URI (that identifies a property) • a value URI (that identifies a value) and/or one or more representations of the value (value representations)

  17. Value strings • each value representation may take the form of a value string, a rich value or a related description • each value string is a simple, human-readable string that represents the resource that is the value of the property • each value string may have an associated value string language that is an ISO language tag (e.g. en-GB)

  18. Encoding schemes • values and value strings can be ‘qualified’ by using encoding schemes • a vocabulary encoding scheme is used to indicate the class of the value • e.g. the value is taken from LCSH • a syntax encoding scheme is used to indicate how the value string is structured • e.g. the value string is a date structured according to the W3CDTF rules (“2004-10-12”)

  19. Description sets • real-world metadata applications tend to be based on loosely grouped sets of descriptions (where the described resources are typically related in some way) • known in the abstract model as description sets • for example, a description set might comprise descriptions of both a painting and the artist

  20. Records • description sets are instantiated, for the purposes of exchange between software applications, in the form of metadata records • each record conforms to one of the DCMI encoding guidelines (XHTML meta tags, XML, RDF/XML, etc.) <dc:title> a document </dc:title> <dc:creator> andy powell </dc:creator> record

  21. 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)

  22. Description rdf:type vocabularyEncodingSchemeURI propertyURI rdfs:label valueURI “value string” propertyURI rdfs:label resourceURI valueURI “value string” valueURI propertyURI

  23. Statement statement rdf:type vocabularyEncodingSchemeURI propertyURI rdfs:label valueURI “value string” propertyURI rdfs:label resourceURI valueURI “value string” statement valueURI propertyURI statement

  24. Vocabulary encoding scheme URI rdf:type vocabularyEncodingSchemeURI propertyURI rdfs:label resourceURI valueURI “value string”

  25. Value string propertyURI rdfs:label resourceURI valueURI “value string”

  26. Value string – where property domain is rdfs:Literal propertyURI resourceURI “value string”

  27. Rich representation propertyURI rdfs:label resourceURI valueURI “value string”^^rdfDatatypeURI

  28. Syntax encoding scheme URI propertyURI rdfs:label resourceURI valueURI “value string”^^syntaxEncodingSchemeURI

  29. Value string languages propertyURI rdfs:label resourceURI valueURI “value string”@en

  30. Related description propertyURI rdfs:label resourceURI valueURI “value string” propertyURI rdfs:label “value string” propertyURI rdfs:label “value string” related description

  31. DC RDF Taskforce • Clarification of the recommendations for encoding 'value strings' in DC RDF/XML • Guidelines for encoding DC metadata using the RDF Model • DC Property Domains and Ranges • Proposed changes to DCMI property definitions • DCMI Term Decision Tree

  32. Domains and ranges • ‘domain’ – the class of resources that a property can be used to describe • ‘range’ – the class of resources that are allowed as values of a property • example: what are the domain and range of dc:creator • domain = NonAgentResource • range = Agent • making explicit what has been implicit until now

  33. DC RDF Taskforce • Clarification of the recommendations for encoding 'value strings' in DC RDF/XML • Guidelines for encoding DC metadata using the RDF Model • DC Property Domains and Ranges • Proposed changes to DCMI property definitions • DCMI Term Decision Tree

  34. Revising DC definitions • revising the language of the definitions to align them with the DCMI Abstract Model • for example dc:relation • was: A reference to a related resource • change to: A related resource • domain: Resource • range: Resource • also note issue with use of ‘content of the resource’ in definitions

  35. DC RDF Taskforce • Clarification of the recommendations for encoding 'value strings' in DC RDF/XML • Guidelines for encoding DC metadata using the RDF Model • DC Property Domains and Ranges • Proposed changes to DCMI property definitions • DCMI Term Decision Tree

  36. Term decision tree • how do you know if something is usable in DC metadata descriptions or not? • has it been explicitly declared as an element, element refinement or encoding scheme? • has it been assigned a unique URI? • is the declaration available at that URI? • if the answers are all ‘yes’, then the thing can be used in DC metadata

  37. Workplan for 2006

  38. Workplan - taskforce • develop short document for RDF implementers, clarifying the resource vs. literal string value issue and providing advice on best practice • consider possible RDF encoding changes (in light of above issue), carry out impact analysis and make recommendations

  39. Workplan – tidying up • finalise provision of a persistent URI for the latest version of our XML schemes • finalise revisions to the Guidelines for implementing Dublin Core in XML document • finalise revisions to the Namespace Policy for the Dublin Core Metadata Initiative (DCMI)

  40. Workplan – new stuff • evaluate use of GRDDL as mechanism for transforming arbitrary DC/XML documents into RDF (DCMI AM) • monitor W3C developments for RDF in XHTML and revise current DC/XHTML guidelines as necessary • develop model of ‘application profiles’ • representing Box/Period/Point in DCAM/RDF

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