Registry of MEG-related schemas MEG BECTa, Coventry, 17 July 2001 Pete Johnston UKOLN, University of Bath Bath, BA2 7AY UKOLN is supported by: URL

MEG,BECTa,Coventry, 17 July Registry of MEG-related metadata schemas How metadata schemas are used Types of schemas Schema registries and their uses Some issues

MEG,BECTa,Coventry, 17 July How metadata schemas are used Implementers use standard schemas in pragmatic way Standards creators –integrity of model, consensus, commonality, interoperability Implementers –service delivery, specificity, localisation Standard solutions published Implementer adaptations/extensions not widely available

MEG,BECTa,Coventry, 17 July Types of schemas Namespace schema –a type of schema –only declare names and definitions Application profile –a type of schema –describes use of terms by application

MEG,BECTa,Coventry, 17 July 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

MEG,BECTa,Coventry, 17 July Machine-readable schemas Namespace schema –RDF Schema –RDF/XML representation Application profile –(presently) no standard convention –SCHEMAS project developing RDF-based convention –XML schema approach possible? –explicit cross reference from description of element use in AP to declaration in NS

MEG,BECTa,Coventry, 17 July 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?

MEG,BECTa,Coventry, 17 July 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

MEG,BECTa,Coventry, 17 July 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

MEG,BECTa,Coventry, 17 July Recent entries in MEG registry MILO –namespace schema –application profile QCA/National Curriculum –namespace schema –application profile Virtual Teacher Centre –namespace schema –application profile

MEG,BECTa,Coventry, 17 July Users of a 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 N.B. Desire registry human-readable only

MEG,BECTa,Coventry, 17 July Users of a schemas registry (2) 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….

MEG,BECTa,Coventry, 17 July Thick registry : database Thick Registry Namespace schema App profile Sample data Mapping Usage guide Software tools Users

MEG,BECTa,Coventry, 17 July Thin registry : portal Thin Registry Namespace schema App profile Sample data Mapping Usage guide Software toolsUsers

MEG,BECTa,Coventry, 17 July 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

MEG,BECTa,Coventry, 17 July Some issues DESIRE registry –human readable only SCHEMAS project –human and machine readable Concepts still evolving Scope of registries? –finding (the right) registry? Communicating with a registry? –functions required? minimal functionality? –interfaces for registries? –describing registries?

MEG,BECTa,Coventry, 17 July Acknowledgements / further reading Rachel Heery & Manjula Patel, Application Profiles Tom Baker, A Grammar of Dublin Core Stuart Weibel, The DCMI: Status & Plans (2001) Jane Hunter, Combining RDF and XML Schemas…. hunter/www10/paper.html SCHEMAS project: DCMI Registry: