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UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk http://www.ukoln.ac.uk/ UKOLN is funded by the British Library Research and Innovation Centre, the Joint Information Systems Committee of the Higher Education Funding Councils, as well as by project funding from the JISC’s Electronic Libraries Programme and the European Union. UKOLN also receives support from the University of Bath where it is based.
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UKOLUG - July 1998 2 Metadata applications resource discovery site-maps content rating e-commerce, rights management collaboration privacy Web-site management W3C’s Resource Description Framework (RDF) provides a generic metadata architecture
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UKOLUG - July 1998 3 Outline... what is RDF? model syntax metadata schemas what is the Dublin Core? Dublin Core in RDF some examples current status of RDF conclusions
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UKOLUG - July 1998 4 What is RDF? Resource Description Framework Input from various communities Platform for Internet Content Selection (PICS) Web Collections (Site maps, MCF) Libraries, museums, archives (DC) Privacy (P3P) W3C Metadata Activity Model and Syntax WG Schema WG Interoperability of metadata semantics, structure, syntax
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UKOLUG - July 1998 5 RDF - the model based on mathematical model arc-node diagrams Web resources represented by nodes with URI collections of properties known as ‘descriptions’ Resource PropertyType Value Property
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UKOLUG - July 1998 6 RDF - simple example or, in plain English… “Andy Powell is the author of the resource identified by http://www.ukoln.ac.uk/metadata/” http://www.ukoln.ac.uk/metadata/ Author Andy Powell
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UKOLUG - July 1998 7 RDF - structured example provide structured metadata by replacing simple text value by another node. http://www.ukoln.ac.uk/metadata/ Author Andy Powella.powell@ukoln.ac.uk NameEmail
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UKOLUG - July 1998 8 RDF - reification possible to make statements about properties process known as reification http://somewhere.com/page.html Cost £0.05 1998-09 ValidUntil
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UKOLUG - July 1998 9 RDF - serialisation syntax serialisation syntax based on XML allows us to write down the RDF model in a way that can be processed by machines http://www.ukoln.ac.uk/metadata/ Title The UKOLN Metadata Home Page Title <RDF:Description RDF:HREF=”http://www.ukoln.ac.uk/metadata/”> The UKOLN Metadata Home Page
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UKOLUG - July 1998 10 RDF - serialisation syntax http://www.ukoln.ac.uk/metadata/ Title The UKOLN Metadata Home Page Title <RDF:Description RDF:HREF=”http://www.ukoln.ac.uk/metadata/”> The UKOLN Metadata Home Page
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UKOLUG - July 1998 11 RDF - serialisation syntax http://www.ukoln.ac.uk/metadata/ Title The UKOLN Metadata Home Page Title <RDF:Description RDF:HREF=”http://www.ukoln.ac.uk/metadata/”> The UKOLN Metadata Home Page
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UKOLUG - July 1998 12 RDF - serialisation syntax http://www.ukoln.ac.uk/metadata/ Title The UKOLN Metadata Home Page Title <RDF:Description RDF:HREF=”http://www.ukoln.ac.uk/metadata/”> The UKOLN Metadata Home Page
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UKOLUG - July 1998 13 RDF - multiple properties <RDF:Description RDF:HREF=”http://www.ukoln.ac.uk/metadata/”> The UKOLN Metadata Home Page Dublin Core, MARC, TEI, IAFA, … Start of several Web pages about metadata Here is an example of a description with multiple properties:
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UKOLUG - July 1998 14 RDF - review what does ‘Title’ mean? is your ‘Title’ the same as my ‘Title’? So, we’ve looked at simple arc-node diagrams and serialisation in XML… but...
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UKOLUG - July 1998 15 RDF - namespaces XML namespaces are used to uniquely identify each PropertyType namespaces prefix the PropertyType separated by ‘:’, e.g. some title each namespace has URI associated with it to ensure uniqueness
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UKOLUG - July 1998 16 RDF - schemas RDF Schemas define: available PropertyTypes within a particular metadata system structure allowable values semantics a Schema Definition Language is currently being defined by the W3C namespace URIs may point to schema definitions
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UKOLUG - July 1998 17 What is the Dublin Core? 15 element metadata set resource discovery Web-based document-like objects emphasis on semantics widespread consensus several syntaxes currently set to become an early example of an RDF schema
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UKOLUG - July 1998 18 DC history... workshop series - DC-1 to DC-5 email discussion list DC Policy Advisory Committee DC Technical Advisory Committee series of 5 RFCs in preparation submission to NISO (…ISO)
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UKOLUG - July 1998 19 Dublin Core - elements Title Subject Description Creator Publisher Contributor Date Type Format Identifier Source Language Relation Coverage Rights 15 element core metadata set
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UKOLUG - July 1998 20 Qualified DC DC semantics are defined very broadly. Possible to: refine the meaning of elements using ‘type’: Relation TYPE=IsPartOf associate value with externally defined ‘scheme’: Subject SCHEME=LCSH Date SCHEME=ISO 8601 indicate ‘language’ of value Title LANGUAGE=en
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UKOLUG - July 1998 21 How is DC currently used? Embedded into HTML Web pages tag limited functionality no structure version 4.0 support for SCHEMEs syntax for qualified DC in tags not well established
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UKOLUG - July 1998 22 DC in HTML UKOLN Home Page...
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UKOLUG - July 1998 23 DC in RDF http://www.ukoln.ac.uk/metadata/ The UKOLN Metadata Home Page DC:Title <RDF:Description RDF:HREF=”http://www.ukoln.ac.uk/metadata/”> The UKOLN Metadata Home Page
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UKOLUG - July 1998 24 DC in RDF http://www.ukoln.ac.uk/metadata/ The UKOLN Metadata Home Page DC:Title <RDF:Description RDF:HREF=”http://www.ukoln.ac.uk/metadata/”> The UKOLN Metadata Home Page
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UKOLUG - July 1998 25 DC in RDF http://www.ukoln.ac.uk/metadata/ The UKOLN Metadata Home Page DC:Title <RDF:Description RDF:HREF=”http://www.ukoln.ac.uk/metadata/”> The UKOLN Metadata Home Page
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UKOLUG - July 1998 26 RDF - current status Some support for RDF in Mozilla (Netscape source code release) RDF toolkits under development Several RDF editors available, e.g. DC-dot, UKOLN Reggie, DSTC http://www.ukoln.ac.uk/metadata/dcdot/ http://metadata.net/dstc/ W3C Syntax and Schema drafts still undergoing development http://www.w3.org/RDF/
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UKOLUG - July 1998 27 Browser Support for RDF Mozilla supports site maps in RDF, as well as bookmarks and history lists See Netscape or HotWired home page for a link to the RDF file. Trusted 3rd Party Metadata Embedded Metadata e.g. sitemaps Image from http://purl.oclc.org/net/eric/talks/www7/devday/
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UKOLUG - July 1998 28 Conclusions RDF is a general-purpose framework RDF provides structured, machine- understandable metadata for the Web metadata vocabularies can be developed without central coordination RDF Schemas describe the meaning of each property name Dublin Core is one of the key RDF Schemas signed RDF is the basis for trust
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