rdf and metadata andy powell ukoln, university of bath [email protected] ukoln is funded by the...

RDF and Metadata

Andy Powell

UKOLN, University of Bath

[email protected]

http://www.ukoln.ac.uk/

UKOLN is funded by the Library and Information Commission, the JointInformation Systems Committee of the Higher Education Funding Councils, aswell as by project funding from the JISC and the European Union. UKOLN alsoreceives support from the University of Bath where it is based.

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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


Presentation outline...

• what is RDF?• model• syntax• metadata schemas

• what is the Dublin Core?• Dublin Core in RDF• some examples• current status of RDF• conclusions


What is metadata?

• data about data?• information about resources?• structured information about ‘stuff’

• ‘stuff’ includes Web resources, books, museum artifacts, CDs, abstract ‘works’, pieces of music…

• machine readable• supports variety of usage scenarios


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


RDF - the model

• simple triple-based model• arc-node diagrams• resources represented by nodes with URI• property is some attribute of the resource• value can be literal or further statement(s)• a collection of statements about a resource

forms a ‘description’

resourceproperty

value

statement


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


RDF - structured example

• provide structured metadata by replacing simple text value by another node.

http://www.ukoln.ac.uk/metadata/author

Andy Powell [email protected]

name emailAddress


RDF - reification

• possible to make statements about statements

• process known as reification

http://somewhere.com/page.htmlcost

£0.05

1999-09

validUntil

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RDF - serialisation syntax

• 2 XML serialisation syntaxes• 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 HomePage

<rdf:RDF> <rdf:Description about=”http://www.ukoln.ac.uk/metadata/”> <title>The UKOLN Metadata Home Page</title> </rdf:Description></rdf:RDF>

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Metadata HomePage


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Metadata HomePage


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Metadata HomePage

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RDF - multiple properties

<rdf:RDF> <rdf:Description about=”http://www.ukoln.ac.uk/metadata/”> <title>The UKOLN Metadata Home Page</title> <keywords>Dublin Core, MARC, TEI, IAFA, … </keywords> <description> Start of several Web pages about metadata </description> </rdf:Description></rdf:RDF>

Here is an example of a description with multiple properties:

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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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RDF - namespaces

XML namespaces are used to uniquely

identify each RDF property• namespaces prefix the property• separated by ‘:’, e.g.

<ukoln:title>some title</ukoln:title>

• each namespace has URI associated with it to ensure uniqueness

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RDF - schemas

• RDF Schemas define:• available properties within a particular metadata

system• structure• allowable values• semantics• relationships between different schemas

• an RDF Schema Specification is currently being finalised by the W3C

• namespace URIs may point to schema definitions

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What is the Dublin Core?

• 15 element metadata set• primarily resource discovery• primarily Web-based document-like

objects• emphasis on semantics• widespread consensus• several syntaxes currently• early example of an RDF schema

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DC history...

• workshop series - DC-1 to DC-5• email discussion list• DC Policy Advisory Committee• DC Technical Advisory Committee• series of RFCs in preparation• submission to NISO (…ISO)

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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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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=ISO8601

• indicate ‘language’ of value• Title LANGUAGE=en

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How is DC currently used?

Embedded into HTML Web pages• <META> tag• limited functionality

• no structure

• HTML version 4.0 support for SCHEME and LANG

• syntax for qualified DC in <META> tags not well established

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DC in HTML<HTML><HEAD>

<TITLE>UKOLN Home Page</TITLE>

<META NAME="DC.Title” CONTENT="UKOLN: UK Office for Library and Information Networking">

<META NAME="DC.Subject" CONTENT="national centre, network information support, library community, awareness, research, information services, public library networking, bibliographic management, distributed library systems, metadata, resource discovery, conferences, lectures, workshops">

<META NAME="DC.Description" CONTENT="UKOLN is a national centre for support in network information management in the library and information communities. It provides awareness, research and information services">

<META NAME="DC.Creator" CONTENT=”UKOLN Information Services Group">

</HEAD>

...

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DC in RDF

http://www.ukoln.ac.uk/metadata/The UKOLN

Metadata HomePage

dc:title

<rdf:RDF

<rdf:Description about=”http://www.ukoln.ac.uk/metadata/”> <dc:title>The UKOLN Metadata Home Page</dc:title> </rdf:Description></rdf:RDF>

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DC in RDF


Metadata HomePage

dc:title

<rdf:RDF

xmlns:dc="http://purl.org/dc/elements/1.0/"> <rdf:Description about=”http://www.ukoln.ac.uk/metadata/”> <dc:title>The UKOLN Metadata Home Page</dc:title> </rdf:Description></rdf:RDF>

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DC in RDF


Metadata HomePage

dc:title

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc="http://purl.org/dc/elements/1.0/"> <rdf:Description about=”http://www.ukoln.ac.uk/metadata/”> <dc:title>The UKOLN Metadata Home Page</dc:title> </rdf:Description></rdf:RDF>

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DC in RDF


Metadata HomePage

dc:title

<?xml version="1.0"?><rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc="http://purl.org/dc/elements/1.0/"> <rdf:Description about=”http://www.ukoln.ac.uk/metadata/”> <dc:title>The UKOLN Metadata Home Page</dc:title> </rdf:Description></rdf:RDF>

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DC in RDF in HTML !

• can’t embed ‘standard’ RDF/XML syntax because content not hidden

• embed using ‘abbreviated syntax’• embed at end of HTML <HEAD> section• if this isn’t possible <LINK> to external

RDF file, e.g.

<LINK rel="meta" href="mydocMetadata.dc.rdf">

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DC in RDF - abbreviated


Metadata HomePage

dc:title

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc="http://purl.org/dc/elements/1.0/"> <rdf:Description about="http://www.ukoln.ac.uk/metadata/" dc:title="The UKOLN Metadata Home Page" /></rdf:RDF>

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RDF - current status

• RDF Specification - W3C Recommendation

• RDF Schema Spec - Proposed Recommendation

• Some support for RDF in Mozilla• RDF toolkits/parsers under development

http://www.w3.org/RDF/Implementations/SiRPAC/• Several RDF editors available, e.g.

• DC-dot, UKOLN• Reggie, DSTC

http://www.ukoln.ac.uk/metadata/dcdot/

http://metadata.net/dstc/

• Various other RDF-based services

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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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Further informationResource Description Framework (RDF) Model and Syntax Specificationhttp://www.w3.org/TR/REC-rdf-syntax/

Resource Description Framework (RDF) Schema Specificationhttp://www.w3.org/TR/PR-rdf-schema/

Dublin Corehttp://purl.org/dc/

DC-Datamodel homehttp://www.mailbase.ac.uk/lists/dc-datamodel/

INDECShttp://www.indecs.org/

DC-dothttp://www.ukoln.ac.uk/metadata/dc-dot/

Reggiehttp://metadata.net

SiRPAChttp://www.w3.org/RDF/Implementations/SiRPAC/http://www.ukoln.ac.uk/metadata/resources/rdf/parser/

Representing vCard v3.0 in RDFhttp://www.dstc.edu.au/RDU/RDF/draft-iannella-vcard-rdf-00.txt

rdf and metadata andy powell ukoln, university of bath [email protected] ukoln is funded by the...

Documents

rdf schema slide

syntax slide

rdf model

rdf schemas rdf schemas

structured metadata

rdf review

element metadata

en slide