DC Architecture WG meeting

1. DC Architecture WG meeting DC-2006, Mexico Tuesday Oct 3 16.30 - 18.30

2. Agenda • introductory session • where we’ve been and where we are going • but not a tutorial • 5 minute break • advanced session • meeting of the working group • detailed discussion about DC Abstract Model, DC-RDF, DC-XML

3. Aims • knowledge sharing • discussion of issues • do the proposed revisions to abstract model address concerns that have been raised • relationship between DCAM and SKOS • consider nature of our DC-XML guidelines • intention is to inform the next iteration of the working drafts

4. Important • this meeting is intended to be informal and interactive • please ask questions if you don’t understand • please raise issues if you disagree • introduce yourself before speaking

5. Session leaders • Andy Powell • chair of DC Architecture / DC Abstract Model • Pete Johnston • author of DC-XML / DC Abstract Model • Mikael Nilsson • author of DC-RDF / DC Abstract Model • Tom Baker • chair of DC Usage Board

6. Agenda • review of progress during the year • summary of DCMI Abstract Model, DC-RDF and DC-XML • note about related Usage Board activities • DC-Architecture and Usage Board roadmap for next year

7. Progress - DC-XML • Guidelines for implementing Dublin Core in XML • DCMI Recommendation, April 2003 • pre-dates development of DCAM • uses two earlier, simpler “abstract models” • “Simple DC” model can be mapped to DCAM description model • “Qualified” model can not be mapped to DCAM description model

8. DC-XML (2) • no DCMI guidance for representing DC description sets using XML • March 2006: DCMI contract to produce revised XML format • working draft issued for comment • comments currently being addressed

9. Progress DC-RDF

10. Mikael Nilsson mini@nada.kth.se The Knowledge Management Research Group Royal Institute of Technology, Stockholm http://kmr.nada.kth.se DC-Architecture WGDC-RDF updates

11. New DC-RDF Working Draft! • Successful public comment in June, 2006 • Will be revised and discussed more • If accepted, will replace • Expressing Simple Dublin Core in RDF/XML, a DCMI Recommendation from July 2002; • Expressing Qualified Dublin Core in RDF / XML, a DCMI Proposed Recommendation from May 2002.

12. Main features • a unified specification for Dublin Core in RDF • full support for the DCMI Abstract Model • good integration with other RDF metadata • supports domains and ranges • <http://www.example.com> dcterms:creator "John Smith" – no longer valid! • much more regular – many complicated options deprecated

14. Progress - Abstract Model • DCMI Abstract Model has generated comments from: • DCMI Usage Board • DCMI Working Groups, particularly WGs developing DCAPs • implementers of DCAPs • developers/implementers of related specs (e.g. SKOS) • researchers • implementers of metadata registries • authors/editors of “encoding guidelines” specifications • …

15. Abstract Model (2) • use of DCAM has: • highlighted omissions, ambiguities, redundancies, errors • created better understanding of what is required • emphasised value of an abstract model! • all of which has fed into process for producing draft revised abstract model (see Wiki) • http://dublincore.org/architecturewiki/AMDraftUpdate

16. Progress - Namespace Policy • no real progress! • revised and discussed at DC-Arch meeting last year • pretty much static since then • may be some minor issues around replicating terms from DC namespace to DCTERMS namespace • need to move to recommendation

17. Usage Board activities • in parallel the DC Usage Board has been • working on assigning domains and ranges to DCTERMS • in order to make some of the property semantics explicit in machine-readable form • clarifying whether each of the current encoding schemes is a ‘syntax encoding scheme’ or a ‘vocabulary encoding scheme’

18. Liaison with Swoogle • before assigning domains and ranges we needed to understand how DC properties are currently used in RDF • obtained statistics from Swoogle • e.g. showed that dc:creator mainly used with range of rdfs:Literal • as a result, our current plan is to copy the 15 DCMES properties into the DCTERMS namespace and assign domains and ranges to them there

19. DC Arch and Usage Board Roadmap for next year Tom

20. Usage Board support forDC Architecture developments • September 2006 – Manzanillo • DC-Architecture • DCAM update • Revised DC-RDF, DC-XML, DC-Text • Usage Board • DCMES changes – finalization • Range vocabulary – review definitions, proposed assignments • Existing terms as syntax or vocabulary encoding schemes

21. Usage Board and DC-Architecture:Joint Work Plan • October through December 2006 • DC-Architecture • Prepare DCAM, DC-Text, DC-XML, DC-RDF, DCMI Namespace Policy for public comment • Extend DCAM with Vocabulary Model and Profile Model • RDF schemas with ranges for purposes of testing • UB • Prepare range vocabulary for public comment

22. Usage Board and DC-Architecture:Joint Work Plan • January to March 2007 – DCMI • Public comment period for DCAM, etc • Resulting in DCMI Recommendations • User-oriented “how-to” documentation for making profiles and vocabularies • April 2007 – Usage Board • Approve vocabulary range as new DCMI terms • Approve assignment of ranges to existing terms

23. 5 minute break

24. Agenda • Abstract Model • DC-RDF • DC-XML

25. DCMI Abstract Model Pete

26. DCMI Abstract Model: issues and proposed changes DCMI Architecture Working Group DC-2006: Metadata for Knowledge & Learning, Manzanillo, Mexico

27. Background • DCMI Abstract Model • DCMI Recommendation March 2005 • DCAM describes • Components and constructs that make up an information structure (“DC description set”) • How that information structure is to be interpreted • DCAM does not describe how to represent DC description set in concrete form

28. DCAM Description Model • a description set is made up of one or more descriptions • a description is made up of • zero or one resource URI and • one or more statements • a statement is made up of • exactly one property URI and • zero or one reference to a value in the form of a value URI • zero or more representations of a value, each in the form of a value representation • zero or one vocabulary encoding scheme URI • a value representation is either • a value string or • a rich representation • a value string may have an associated value string language • a value string may have an associated syntax encoding scheme URI • a value may be the subject of a related description

29. Description Set Description Resource URI Property URI Property URI Value URI Value URI Vocab Enc Scheme URI Vocab Enc Scheme URI Property URI Value string Value string Value string Syntax Enc Scheme URI Syntax Enc Scheme URI Syntax Enc Scheme URI Statement Property URI Property URI Rich representation Rich representation Resource URI Property URI

30. DCMI Abstract Model in use • Use of DCAM has generated comments from e.g. • DCMI Usage Board • DCMI Working Groups, particularly WGs developing DCAPs • Implementers of DCAPs • Developers/implementers of related specs (e.g. SKOS) • Researchers • Implementers of metadata registries • Authors/editors of “encoding guidelines” specifications • (and others!) • Use of DCAM has • highlighted omissions, ambiguities, redundancies, errors • created better understanding of what is required • emphasised value of an abstract model!

31. Proposed changes • Issues collated in • http://dublincore.org/architecturewiki/AMIssues • Some editorial/presentational change • Remove some historical information • Clarify existing concepts/constructs • Extend to include new concepts/constructs

32. Editorial/presentational change • Purpose of DCAM • (Current) “The primary purpose of this document is to provide a reference model against which particular DC encoding guidelines can be compared. To function well, a reference model needs to be independent of any particular encoding syntax. ” • Doesn’t reflect role of DCAM in defining what DC metadata is, the nature of the components used, and how they are interpreted • Also DCAM should be starting point for “encoding guidelines” • (Proposed) “The primary purpose of this document is to specify the components and constructs used in Dublin Core metadata. It defines the nature of the components used and describes how those components are combined to create information structures. It provides a reference model which is independent of any particular encoding syntax.”

33. Editorial/presentational change • Vocabulary Model • Description of types of terms and types of relationships that exist between terms • Based on RDF Schema • Currently embedded in “Resource Model”/Figure 1 • Useful to make more explicit • Also some extensions required (more later)

34. Remove some historical information • Appendices contain discussion of specs based on earlier/different “abstract models” • e.g. appendices on encoding guidelines in 2003 • attempts to retrofit DCAM confusing (inaccurate?) • redundant once DCMI adopts encoding guidelines based on DCAM • Confused terminology in discussion of “structured values” • addressed in revisions to DCSV, Box, Period, Point (2006) • Useful for context of DCAM in 2003, but should not be part of document

35. Clarify existing concepts/constructs • Phrasing of some definitions is inconsistent with usage in text e.g. • Term • (Current) The generic name for a property (i.e. element or element refinement), vocabulary encoding scheme, syntax encoding scheme or concept taken from a controlled vocabulary (concept space). • (Proposed) A property (i.e. element or element refinement), vocabulary encoding scheme, syntax encoding scheme or concept taken from a controlled vocabulary (concept space).

36. Clarify existing concepts/constructs • Sub-property/Sub-class • Currently modelled as distinct classes • Should be represented in Vocabulary Model as relationships between properties, classes • i.e. same concepts as in RDF Schema • Also provide definitions in glossary

37. Clarify existing concepts/constructs • “Description Set” • Need to emphasise that “description set” is primary “abstract information structure” • Proposal: Add “A description set is a set of one or more descriptions” to textual description of description model • “Related description” • Need to emphasise that a “related description” is just a description • Proposal: use “description of value” etc • “Resource”/”Resource URI” and “Value”/”Value URI” • A value is a resource, so sometimes use of “resource” seems ambiguous • Proposal: use “described resource” to refer to subject of description

38. Clarify existing concepts/constructs • Value strings, language tags & syntax encoding schemes • (Currently) allow value string to be associated with both a language tag and a syntax encoding scheme (datatype) • Proposal: permit value string to be associated with either language tag or syntax encoding scheme, or neither, but not both • “Empty statements” • (Currently) allow a statement with no value URI or value representation and no (“related”) description of value • Proposal: specify that value URI or value representation must be provided unless value is subject of separate description

39. Clarify existing concepts/constructs • Syntax encoding schemes • (Currently) A syntax encoding scheme indicates that the value string is formatted in accordance with a formal notation, such as "2000-01-01" as the standard expression of a date. • SES includes a “contract” for interpretation of literal • But “formatted” too narrow • ISO 3166, xsd:Boolean, xsd:int • Doesn’t capture notion that SES indicates that literal “stands for” something else • Proposal: A syntax encoding scheme is a set of strings that is associated with a set of rules which describe a mapping between that set of strings and a set of resources. The mapping rules may be based on a description of how the string is structured (e.g. DCMI Box) or they may be based on a simple enumeration of all the strings and the corresponding resource (e.g. ISO 3166).

40. Extend to include new concepts/constructs • Range/domain • DCMI plans to make range/domain assertions for DCMI-owned properties • Making explicit to software what is implicit in human-readable descriptions • Should be added to Vocabulary Model as relationships between properties, classes • i.e. same concepts as in RDF Schema • Also provide definitions in glossary

41. Extend to include new concepts/constructs • Vocabulary Encoding Scheme v Class of Value • (currently) VES = class of Value • Conflict with existing DCMI use of concept e.g. • class of LCSH terms considered a VES • class of collections or class of persons not considered VES • Also integration with SKOS • relation between Concept and ConceptScheme is skos:inScheme not rdf:type (instance-of) • so difficult to use same resource as skos:ConceptScheme and as VES • What distinguishes a VES from a Class? • Proposal: VES as enumerable set of resources • Proposal: Add Value Class URI to description model (in addition to VES URI)

42. Other issues not yet discussed • Rich Representations & MIME types • Should DCAM description model specify that rich representation should be associated with MIME type? • “Conformance to DCAM”

43. DCMI Abstract Model: issues and proposed changes DCMI Architecture Working Group DC-2006: Metadata for Knowledge & Learning, Manzanillo, Mexico

44. Encoding guidelinesDC-RDF Mikael

45. Encoding guidelinesDC-XML Pete

46. Expressing DC metadata in XML: a status report to DCMI Architecture WG DCMI Architecture Working Group DC-2006: Metadata for Knowledge & Learning, Manzanillo, Mexico

47. Expressing DC metadata in XML • Background • DC-XML 2006-05-29 • public comment version • DC-XML 2006-07-04 • draft to DC Arch WG • verbosity, human readability, “hard to explain” • no “term-level” validation with W3C XML Schema • DC-XML-Full 2006-09-18 • draft to DC Arch WG • extension to DC-XML 2006-07-04 • DC-XML-Min 2006-09-18 • draft to DC Arch WG • supports subset of DCAM description model • Moving forward?

48. Background • DCMI Abstract Model • DCMI Recommendation March 2005 • DCAM describes • Components and constructs that make up an information structure (“DC description set”) • How that information structure is to be interpreted • DCAM does not describe how to represent DC description set in concrete form

49. Description Set Description Resource URI Property URI Property URI Value URI Value URI Vocab Enc Scheme URI Vocab Enc Scheme URI Property URI Value string Value string Value string Syntax Enc Scheme URI Syntax Enc Scheme URI Syntax Enc Scheme URI Statement Property URI Property URI Rich representation Rich representation Resource URI Property URI

50. Background • Guidelines for implementing Dublin Core in XML • DCMI Recommendation, April 2003 • Pre-dates development of DCAM • Uses two earlier, simpler “DC abstract models” • “Simple DC metadata record” model can be mapped to DCAM description model • “Qualified DC metadata record” model can not be mapped to DCAM description model • No DCMI guidance for representing DC description sets using XML • March 2006: DCMI contract to produce revised XML format