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Metadata Schema Registries: background and context MEG Registry Workshop, Bath, 21 January 2003

Explore the importance of schema registries in enabling metadata interoperability, sharing, and schema navigation. Learn about application profiles and element sets for creating coherent metadata. Discover how schema registries support evolution and alignment in metadata standards.

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Metadata Schema Registries: background and context MEG Registry Workshop, Bath, 21 January 2003

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  1. Metadata Schema Registries:background and contextMEG Registry Workshop, Bath, 21 January 2003 Rachel Heery UKOLN, University of Bath Bath, BA2 7AY r.heery@ukoln.ac.uk http://www.ukoln.ac.uk/ UKOLN is supported by:

  2. Proliferation of metadata • Increase in web based activity reliant on metadata • Corporate portals • Subject portals (gateways) • eCommerce • eScience • Rights • Open archives • Etc etc • An appropriate element set is required for every implementation….

  3. Interoperability and differentiation • Implementers must decide on appropriate metadata for a new service or system ….. but what?Is there a single answer? • Implementors approve of re-use where appropriate • Implementors acknowledge importance of interoperability • End-users want coherent services • …. But all want new, innovative services • Tension between alignment and differentiation

  4. Metadata for Education Group • UK educational organisations and initiatives >60 • Common interest in description and provision of educational resources • Creating schemas to describe educational resources >20 • Potential for sharing and collaboration

  5. Definition of Element Set • An element set is coherent bounded set of terms formulated as a basis for metadata creation • Designed for particular purpose e.g. domain-specific, resource description, rights • Identifies designated authority

  6. Example element sets • DCMI Elements and Element Refinements • MARC • IEEE LOM • GILS • MPEG-7 • vCARD

  7. Definition of Application Profile • An application profile is an element set optimised for a particular local application. It may include data elements (terms) drawn from one or more element sets. • Application profiles are declarations of usage • Application profile reuse data elements already defined elsewhere; or use data elements from a local element set

  8. Example Application profiles • Renardus European Subject Gateway • Australian Government Locator Service • Food and Agricultural Organisation • European Environment Agency • Various UK educational initiatives • Qualifications and Curriculum Authority • Virtual Teacher Centre • DCMI Application Profiles • Government, Libraries, Education

  9. Definition of Schema • A schema is a structured representation that defines and identifies data elements in an element set • Provides authoritative declaration of semantics of terms • Indicates semantic relationship between terms • Supports unique identification of terms • Schema can be expressed formally in RDF or XML schema language

  10. Element Set Declares set of terms with identifiers, definitions and comments Self reliant Means of defining and identifying ‘new terms’ Application profile Re-uses terms from element sets Specifies terms used in particular application or domain Optimised for that application or domain Means of declaring terms that an application uses and understands In summary

  11. Typology of metadata Application Profile 1 Element set 1 uses data element A data element A uses data element B data element B uses data element C data element C data element D Element set 2 Application Profile 2 data element E uses data element D data element F uses data element G data element G uses data element H data element H

  12. Registries: enabling discovery and re-use of existing schemas • Ambition: To promote re-use and interoperability whilst enabling a common approach to extensibility and localisation • To build a ‘schema navigation service’ which will provide information about existing element sets and facilitate re-use • To encourage ‘declaring and sharing’ of data elements, element sets and application profiles

  13. Sharing schemas... • Standard solutions are published but • Implementor adaptations/extensions are not made widely available • Need to avoid proliferation of schemas, to avoid duplication and repetition

  14. Declaring application profiles • Why? • To inform and promote existing schemas • To provide authoritative versions • To facilitate inter-working • To support • Evolution • Alignment

  15. Characterising requirements • Implementors need to declare various characteristics of their schema: • Terms used • Whether a term is mandatory • Any refined definitions of terms from existing element sets • Which schemes must be used for content • other rules for content

  16. Schema registries • To give access to schemas • searching and browsing • names, definitions, usage • relationships between terms • Support evolution of schemas • top-down (standards authorities) • bottom-up (real world usage) • Disclosure, discovery, effective reuse, harmonisation

  17. Previous Registry activity • Establishing data models for declaring schemas and local usage • DESIRE Registry, MetaForm • Investigating RDFS, and adding activity reports • SCHEMAS Registry • Establishing process for Element Set specific Registry • DCMI Registry • …..Trial loading of schemas

  18. DESIRE Registry Based on MySQL Lack of flexibility Need for machine readable interface DCMI Registry Data model Use of RDFS Creating schemas centrally Administrative bottleneck Keeping registry up-to-date Schema creators have knowledge of schemas, not central administrator Issues to address

  19. Aims of MEG Registry project • To provide complementary creation tool and registry • Providing interactive environment for schema creation • Enable schema creators to declare their own schemas • To create machine readable schemas • With no knowledge of complex schema language • Explore RDFS based solution

  20. Distributed schema creation and registration Other Registries Other Registries Other Registries MEG Schema Registry MEG Schema creation tool Other Schema creation tools Local application

  21. Difficult issues! • People are keen to reach consensus, but…. • Inconsistent approach in practice • When should implementor create new terms? • When should implementor try to add terms to existing element sets? • Varying practice about creation of local element sets • Messy issue of data models

  22. Planned related activities • CEN-MMI-DC producing a CWA ‘DCMI Application profiles guidelines’ • Draft circulated, due for completion September 2003 • CORES schema creation workshop • March 6/7, SZTAKI, Budapest • DCMI Registry Phase 2 • Requirement Document due end January 2003

  23. URLs • SCHEMAS Registry • http://www.schemas-forum.org • DCMI Registry • http://dublincore.org/dcregistry/index.html • CORESRegistry • http://www.cores-eu.net • MEG Registry project http://www.ukoln.ac.uk/metadata/education/regproj/

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