Metadata Schema Registries: background and context MEG Registry Workshop, Bath, 21 January 2003 Rachel Heery UKOLN, University of Bath Bath, BA2 7AY 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 In summary 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

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

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 MEG Schema creation tool MEG Schema Registry Other Registries Local application Other Registries Other Schema creation tools

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 DCMI Registry CORES Registry MEG Registry project