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UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath [email protected] 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.

UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath [email protected] UKOLN

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Page 1: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 19981

Metadata for the WebRDF and the Dublin Core

Andy Powell

UKOLN, University of Bath

[email protected]

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.

Page 2: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 19982

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

Page 3: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 19983

Outline...

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

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

Page 4: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 19984

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

Page 5: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 19985

RDF - the model

• based on mathematical model• arc-node diagrams• Web resources represented by nodes with

URI• collections of properties known as

‘descriptions’

ResourcePropertyType

Value

Property

Page 6: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 19986

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

Page 7: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 19987

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 Email

Page 8: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 19988

RDF - reification

• possible to make statements about properties

• process known as reification

http://somewhere.com/page.htmlCost

£0.05

1998-09

ValidUntil

Page 9: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 19989

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 HomePage

Title

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

Page 10: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 199810

RDF - serialisation syntax

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

Metadata HomePage

Title

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

Page 11: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 199811

RDF - serialisation syntax

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

Metadata HomePage

Title

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

Page 12: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 199812

RDF - serialisation syntax

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

Metadata HomePage

Title

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

Page 13: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 199813

RDF - multiple properties

<RDF:RDF> <RDF:Description RDF:HREF=”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:

Page 14: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 199814

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...

Page 15: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 199815

RDF - namespaces

XML namespaces are used to uniquely

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

<UKOLN:Title>some title</UKOLN:Title>

• each namespace has URI associated with it to ensure uniqueness

Page 16: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 199816

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

Page 17: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 199817

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

Page 18: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 199818

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)

Page 19: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 199819

Dublin Core - elements

• Title • Subject • Description • Creator • Publisher • Contributor • Date • Type

• Format • Identifier • Source • Language • Relation• Coverage • Rights

• 15 element core metadata set

Page 20: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 199820

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

Page 21: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 199821

How is DC currently used?

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

• no structure

• version 4.0 support for SCHEMEs• syntax for qualified DC in <META>

tags not well established

Page 22: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 199822

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>

...

Page 23: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 199823

DC in RDF

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

Metadata HomePage

DC:Title

<RDF:RDF> <RDF:Description RDF:HREF=”http://www.ukoln.ac.uk/metadata/”> <DC:Title>The UKOLN Metadata Home Page</DC:Title> </RDF:Description></RDF:RDF>

Page 24: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 199824

DC in RDF

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

Metadata HomePage

DC:Title

<?xml:namespace ns="http://purl.org/dublin_core/schema/" prefix=”DC"?>

<RDF:RDF> <RDF:Description RDF:HREF=”http://www.ukoln.ac.uk/metadata/”> <DC:Title>The UKOLN Metadata Home Page</DC:Title> </RDF:Description></RDF:RDF>

Page 25: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 199825

DC in RDF

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

Metadata HomePage

DC:Title

<?xml:namespace ns="http://www.w3.org/TR/WD-rdf/" prefix=”RDF"?>

<?xml:namespace ns="http://purl.org/dublin_core/schema/" prefix=”DC"?>

<RDF:RDF> <RDF:Description RDF:HREF=”http://www.ukoln.ac.uk/metadata/”> <DC:Title>The UKOLN Metadata Home Page</DC:Title> </RDF:Description></RDF:RDF>

Page 26: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 199826

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/

Page 27: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 199827

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/Image from http://purl.oclc.org/net/eric/talks/www7/devday/

Page 28: UKOLUG - July 1998 1 Metadata for the Web RDF and the Dublin Core Andy Powell UKOLN, University of Bath a.powell@ukoln.ac.uk  UKOLN

UKOLUG - July 199828

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