Docstoc

Schema Registries and context

Document Sample
Schema Registries and context Powered By Docstoc
					                  PwC



Schema Registries and context

            Rachel Heery, UKOLN
                 r.heery@ukoln.ac.uk


  CORES Schema Creation & Registration Workshop,
    SZTAKI, Budapest, Hungary, 6-7 March 2003
    Proliferation of metadata


    Metadata underlies Web based services
           Enterprise portals
           Subject portals (gateways)
           eCommerce
           eScience
           Rights and conditions of use
           Open archives
           Etc etc

    An appropriate element set is required for every
      implementation….

2                           CORES Schema Creation & Registration Workshop, SZTAKI, Budapest, 6-7 March 2003
    Interoperability and
    differentiation
    Need to manage metadata efficiently and effectively to
      support this range of services
       Facilitate data exchange
       Share and re-use metadata
       Use common tools

    Whilst allowing for
       Extensibility
       Localisation to meet local requirements

    Tension between alignment and differentiation


3                         CORES Schema Creation & Registration Workshop, SZTAKI, Budapest, 6-7 March 2003
    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


4                       CORES Schema Creation & Registration Workshop, SZTAKI, Budapest, 6-7 March 2003
    Definitions…


       Data element
       Element Set
       Application Profile
       Schema
       Metadata instance




5                      CORES Schema Creation & Registration Workshop, SZTAKI, Budapest, 6-7 March 2003
    Data element


        A unit of data for which the definition, identification,
        representation, and permissible values can be specified
       Data elements are ‘properties’ of things
       Data elements can be documented i.e.defined, given
        unique identifiers
       Data elements can be ‘represented’ by different
        syntaxes
       Rules for the value of data elements can be specified,


6                        CORES Schema Creation & Registration Workshop, SZTAKI, Budapest, 6-7 March 2003
    Examples of data elements


       Title
       Author
       Creator
       Abstract




7                  CORES Schema Creation & Registration Workshop, SZTAKI, Budapest, 6-7 March 2003
    Definition of Element Set

       An element set is coherent bounded set of data
       elements (terms) formulated as a basis for metadata
       creation


           Designed for particular purpose e.g. domain-specific,
            resource description, rights
           Identifies designated authority




8                        CORES Schema Creation & Registration Workshop, SZTAKI, Budapest, 6-7 March 2003
    Examples of element sets


       DCMI v1.1
       MARC
       IEEE LOM
       GILS
       MPEG-7?
       vCARD?


9                   CORES Schema Creation & Registration Workshop, SZTAKI, Budapest, 6-7 March 2003
     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. It may specify rules
     for values of elements.

         Application profiles are declarations of usage
         Application profile reuse data elements already
          defined elsewhere; or use data elements from a
          local element set

10                    CORES Schema Creation & Registration Workshop, SZTAKI, Budapest, 6-7 March 2003
     Examples of 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
            Libraries, Government


11                          CORES Schema Creation & Registration Workshop, SZTAKI, Budapest, 6-7 March 2003
Application Profile model
   Element set 1      Application Profile 1

   data element A    uses data element A

   data element B    uses data element B

   data element C    uses 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
     In summary


     Element Set                                   Application Profile
         Declares set of data                         Re-uses terms from element
         elements (terms) with                          sets
         identifiers, definitions and
         comments                                       May specify rules for values

        Self reliant                                  Optimised for particular
                                                        application or domain


                                                       Means of declaring terms that an
        Means of defining and                          application uses and understands
         identifying ‘new data
         elements’


13                            CORES Schema Creation & Registration Workshop, SZTAKI, Budapest, 6-7 March 2003
     Definition of Schema


     A schema is a structured representation that defines
     and identifies the data elements in an element set


            Provides authoritative declaration of semantics of data
             elements
            Indicates semantic relationship between data elements
            Supports unique identification of data elements
            Schema can be expressed formally in RDF or XML
             schema language




14                          CORES Schema Creation & Registration Workshop, SZTAKI, Budapest, 6-7 March 2003
     Extract from schema


     <rdf:Property ID="legalStatus">
     <rdfs:label>Legal Status</rdfs:label>
     <rdfs:comment>A statement of the legal status of the
        collection.</rdfs:comment>
     <rdfs:subPropertyOf
        rdf:resource="http://purl.org/dc/elements/1.1/description" />
     <rdfs:domain rdf:resource="http://dublincore.org/2000/03/13-
        dctype#Collection" />
     <rdfs:isDefinedBy rdf:resource="http://www.schemas-
        forum.org/registry/schemas/RSLP-CLD/1.0/cld" />
     </rdf:Property>


15                          CORES Schema Creation & Registration Workshop, SZTAKI, Budapest, 6-7 March 2003
     Metadata instance


         Data about a particular resource structured
         according to a particular schema and expressed
         in a particular syntax


        Equates to a ‘record’

        Concrete form of element set or application profile




16                        CORES Schema Creation & Registration Workshop, SZTAKI, Budapest, 6-7 March 2003
     Example of instance metadata


       245 00 Wordnews online $h [computer file].
       246 3 World news online
       256   Computer online service.
       260   Washington, D.C. : $b Worldnews Online, $c [1995-
       538   Mode of access: Internet.
       500   Title from title frame.
       520   “WorldNews OnLine is a service … “
       650 0 Newspapers $x Databases.
       856 7 $u http://worldnews.net $2 http




17                           CORES Schema Creation & Registration Workshop, SZTAKI, Budapest, 6-7 March 2003
     Metadata concepts


                              (a) Attribute Space                           (b) Value Space
       Layer 3            e.g LOM, Dublin Core MES,                   e.g. classification schemes,
                                   indecs                               controlled vocabularies,
                                                                               taxonomies

                                                      Representation
       Layer 2
                                                 e.g. XML, RDF, DAML-OIL



                                               Transport and Exchange
       Layer 1                  e.g HTTP Get, OAI Protocol for Metadata Harvesting



      From: Thomas Baker et al., Principles of Metadata Registries, DELOS 2003

18                                      CORES Schema Creation & Registration Workshop, SZTAKI, Budapest, 6-7 March 2003
     Possible functions of Schema
     Registry
          To aid navigation
             • searching and browsing
             • names, definitions, usage
             • relationships between terms
          Support evolution of schemas
             • Versioning, historical record
          Provide mappings
          Provide annotations

       For users who might be
        Tools (metadata editors, metadata validators, conversion tools)
        Humans (developers, implementors, cataloguers)

19                            CORES Schema Creation & Registration Workshop, SZTAKI, Budapest, 6-7 March 2003
     Types of registry: collection
     policy

        Sector or Domain specific
        Enterprise based
        Standards based (DCMI)
        Application profiles
        Functional (rights, resource discovery)




20                      CORES Schema Creation & Registration Workshop, SZTAKI, Budapest, 6-7 March 2003
     Aims of CORES Registry
     project

        Providing interactive environment for schema creation
              Complementary creation tool and registry



        Enable schema creators to declare their own schemas
              To create machine readable schemas
              Users require no knowledge of complex schema language
              Scaleable solution


        Explore open standards solution
              RDFS

        Explore annotation and authentication
21                             CORES Schema Creation & Registration Workshop, SZTAKI, Budapest, 6-7 March 2003
      Distributed schema creation and
      registration

     Other Registries              MEG Schema
     Other Registries
      Other Registries               Registry




                            MEG Schema                       Other Schema creation
                             creation tool                           tools




                           Local applications

22                       CORES Schema Creation & Registration Workshop, SZTAKI, Budapest, 6-7 March 2003
      Distributed schema creation and
      registration

     Other Registries              MEG Schema                          CORES Schema
     Other Registries
      Other Registries               Registry                             Registry




     CORES Schema             MEG Schema                     Other Schema creation
       creation tool           creation tool                         tools




                           Local applications

23                       CORES Schema Creation & Registration Workshop, SZTAKI, Budapest, 6-7 March 2003
     Difficult issues!



        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


24                             CORES Schema Creation & Registration Workshop, SZTAKI, Budapest, 6-7 March 2003
     URLs


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

25                      CORES Schema Creation & Registration Workshop, SZTAKI, Budapest, 6-7 March 2003

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:0
posted:3/31/2011
language:English
pages:25