1. The role of metadata schema registries XML and Educational Metadata, SBU, London, 10 July 2001 Pete Johnston UKOLN, University of Bath Bath, BA2 7AY UKOLN is supported by: Email p.johnston@ukoln.ac.uk URL http://www.ukoln.ac.uk/

2. XML and Educational Metadata, SBU, London, 10 July 2001 2 Metadata schema registries Metadata schemas in the real world A typology of metadata schemas Metadata schema registries Some issues

3. XML and Educational Metadata, SBU, London, 10 July 2001 3 Metadata schemas in real world Implementers use standard schemas in pragmatic way Standards creators –integrity of model –consensus –commonality –interoperability Implementers –service delivery –specificity –localisation

4. XML and Educational Metadata, SBU, London, 10 July 2001 4 Metadata schemas in real world Implementers –combine elements from different sources –create local elements –adapt definitions of elements –constrain use of elements Standard solutions published Implementer adaptations/extensions not widely available

5. XML and Educational Metadata, SBU, London, 10 July 2001 5 Metadata schemas in real world Metadata as language –DC as “pidgin” (Tom Baker) Languages resist stability –Users stretch definitions, coin local terms, customise to needs With schemas, real language use is not made visible –duplication of effort –confusion for implementers

6. XML and Educational Metadata, SBU, London, 10 July 2001 6 A typology of schemas Schemas –declare names and definitions (“semantics”) of terms –various forms Namespace schema –a type of schema –only declare names and definitions Application profile –a type of schema –describes use of terms by application

7. XML and Educational Metadata, SBU, London, 10 July 2001 7 Application profiles (Re)use terms defined in namespace schemas –may combine terms from multiple namespace schemas –may adapt/refine semantic definitions –may specify permitted schemes for values of elements –may mandate element usage, occurrence Set of elements; set of policies defining use; set of guidelines making policies explicit

8. XML and Educational Metadata, SBU, London, 10 July 2001 8 Syntax for schemas Machine readability Namespace schema –RDF Schema –RDF/XML representation Application profile –(presently) no standard convention –SCHEMAS project developing RDF-based convention –explicit cross reference from description of element use in AP to declaration in NS

9. XML and Educational Metadata, SBU, London, 10 July 2001 9 Schemas registries To provide a publication context for namespace schemas & application profiles –standard definitions of terms –by whom? –usage/adaptations of terms –by whom? –annotations, commentaries, evaluations –by whom?

10. XML and Educational Metadata, SBU, London, 10 July 2001 10 Schemas registries (2) To provide a dictionary of terms –names, definitions, usage –relationships between terms Prescribe (standards) and describe (usage) Support evolution of schemas –top-down (standards authorities) –bottom-up (real world usage) Disclosure, discovery, effective reuse, harmonisation

11. XML and Educational Metadata, SBU, London, 10 July 2001 11 Schemas registries (3) Might “contain” –schemas –namespace schemas –application profiles –information about schemas (annotations) –guidelines –evaluations, commentaries etc. –schemes –controlled vocabularies, thesauri –mappings between schemas –pointers –to users, implementers, projects, tools

12. XML and Educational Metadata, SBU, London, 10 July 2001 12 Thick registry : database Thick Registry Namespace schema App profile Sample data Mapping Usage guide Software tools Users

13. XML and Educational Metadata, SBU, London, 10 July 2001 13 Thin registry : portal Thin Registry Namespace schema App profile Sample data Mapping Usage guide Software toolsUsers

14. XML and Educational Metadata, SBU, London, 10 July 2001 14 Users of schemas registry Human –publishers of standards –implementers of AP’s –developers seeking schemas –developers mapping between schemas –researchers studying schemas Functions –Search for schemas, elements –View, navigate schemas –View annotations etc –evaluate

15. XML and Educational Metadata, SBU, London, 10 July 2001 15 Users of schemas registry Software tools e.g. –metadata instance editor –metadata instance validator –metadata transformation/conversion –application profile development tool –… etc! Functions –Retrieve element definition –Retrieve usage description (including vocabularies etc) –Retrieve definition of semantically equivalent term….

16. XML and Educational Metadata, SBU, London, 10 July 2001 16 Technology of registries RDF and RDF(S) provide foundations EOR (Extensible Open RDF) toolkit –Eric Miller (formerly of OCLC) –open source –extensible set of Java classes –support for generic RDF Registry as application built on EOR –harvests RDF schemas –parses, stores, indexes –provides interface for query, navigation

17. XML and Educational Metadata, SBU, London, 10 July 2001 17 Some issues Concepts (e.g. application profile) still evolving! Finding (the right) registry? –scope of registries? Communicating with a registry? –functions required? minimal functionality? –interfaces for registries? –describing registries? Trusting a registry?

18. XML and Educational Metadata, SBU, London, 10 July 2001 18 Acknowledgements / further reading Rachel Heery & Manjula Patel, Application Profiles http://www.ariadne.ac.uk/issue25/app-profiles/ Tom Baker, A Grammar of Dublin Core http://www.dlib.org/dlib/october00/baker/10baker.html Stuart Weibel, The DCMI: Status & Plans (2001) http://www.cimi.org/public_docs/CIMI-2001-06.ppt Jane Hunter, Combining RDF and XML Schemas…. http://archive.dstc.edu.au/RDU/staff/jane- hunter/www10/paper.html SCHEMAS project: http://www.schemas-forum.org/ DCMI Registry: http://dublincore.org/groups/registry/