The role of metadata schema registries XML and

The role of metadata schema registries XML and Educational Metadata, SBU, London, 10 July 2001 Pete Johnston UKOLN, University of Bath, BA 2 7 AY Email p. johnston@ukoln. ac. uk URL http: //www. ukoln. ac. uk/ UKOLN is supported by: XML and Educational Metadata, SBU, London, 10 July 2001

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

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 3 XML and Educational Metadata, SBU, London, 10 July 2001

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 4 XML and Educational Metadata, SBU, London, 10 July 2001

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 5 XML and Educational Metadata, SBU, London, 10 July 2001

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 6 XML and Educational Metadata, SBU, London, 10 July 2001

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 7 XML and Educational Metadata, SBU, London, 10 July 2001

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 8 XML and Educational Metadata, SBU, London, 10 July 2001

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? 9 XML and Educational Metadata, SBU, London, 10 July 2001

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 10 XML and Educational Metadata, SBU, London, 10 July 2001

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 11 XML and Educational Metadata, SBU, London, 10 July 2001

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

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

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 14 XML and Educational Metadata, SBU, London, 10 July 2001

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…. 15 XML and Educational Metadata, SBU, London, 10 July 2001

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 16 XML and Educational Metadata, SBU, London, 10 July 2001

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? 17 XML and Educational Metadata, SBU, London, 10 July 2001

Acknowledgements / further reading Rachel Heery & Manjula Patel, Application Profiles http: //www. ariadne. ac. uk/issue 25/app-profiles/ Tom Baker, A Grammar of Dublin Core http: //www. dlib. org/dlib/october 00/baker/10 baker. 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/janehunter/www 10/paper. html SCHEMAS project: http: //www. schemas-forum. org/ DCMI Registry: http: //dublincore. org/groups/registry/ 18 XML and Educational Metadata, SBU, London, 10 July 2001