Resource Description Framework (RDF)

Course: Electronic Document

Team member:Ding Feng

Ding Wei

Wang Ling

Date: 02.05.2002

Outline

• Introduction

• Benefits

• How RDF works?

• RDF characteristics

• RDF Model

• RDF Schemas

• Describing things with RDF

• History

Introduction

• Machine-understandable information

• Properties of WWW resources

• A framework for describing and interchanging metadata resource propertystatement

• RDF statements specify the properties and values of Web resources

• RDF is encoded in XML • RDF Vocabularies

• Why Not Just Use XML

Benefits

• By providing a consistent framework, RDF will encourage the providing of metadata about Internet resources.

• Because RDF will include a standard syntax for describing and querying data, software that exploits metadata will be easier and faster to produce.

• The standard syntax and query capability will allow applications to exchange information more easily.

• Searchers will get more precise results from searching, based on metadata rather than on indexes derived from full text gathering.

• Intelligent software agents will have more precise data to work with.

How RDF works?

• a formal W3C Recommendation

• part of an Extensible Markup Language (XML) section

• constitute a class of such like descriptions

• classes could fit into a schema or hierarchy of classes

• The schema of classes proposal would save having to repeat descriptions since a single reference to the class of which a particular RDF description was a part would suffice

• The scheme or description of the collection of classes could itself be written in RDF language.

Characteristics

• Independence

• Interchange

• Scalability

• Properties are Resources

• Values Can Be Resources

• Statements Can Be Resources

RDF Data Model

• A model is a set of statements

• Statement: = (predicate, subject, object)

• Predicate is a property

• Subject is a resource

• Object is value

• Object = Predicate(Subject)

RDF Statements

Subject Objectpredicate

Resource(Subject)

Property(Predicate)

Value(Object)

"War and Peace" Author "Leo Tolstoy"

http://www.ccil.org/~cowan

MIME Type "text/html"

http://www.ccil.org/~cowan/XML

Parent http://www.ccil.org/~cowan

RDF Statements

<rdf:Statement>

<rdf:subject resource=“http://www.openhealth.org/RDF/rdfExtractify.xsl”>

<rdf:predicate resource=“http://www.purl.org/dublin-core#author”>

<rdf:object>Jonathan Borden</rdf:object>

</rdf:Statement>

Describing things with RDF

<rdf:Description about=“http://www.openhealth.org/RDF/rdfExtractify.xsl”>

<dc:author>Jonathan Borden</dc:author>

<dc:description>An XSLT based parser which converts an arbitrary XML document into RDF Statements</dc:description>

</rdf:Description>

RDF Schemas

• Describe rules for using RDF properties

• Are expressed in RDF• Provides information about the interpretation of the

statements given in an RDF data model

• Are not to be confused with XML Schemas (eventual DTD replacements)

Simplified Schema

<rdfs:Class rdf:ID=“Provider”>

<rdfs:subClassOf rdf:resource=“#Person”/>

</rdfs:Class>

History

• May 2001: WWW10 W3C's Semantic Web Track and the Semantic Web Developers Day. Hong Kong

• Feb 2001: RDF Interest Group meeting (26-27 Feb 2001)

• Feb 2001: Semantic Web Activity launched

• Oct 1999: "Cambridge Communiqué" W3C NOTE issued on application schema layering

• Sep 2000 XML World 2000 talk: XML and the Web.

• Mar 2000: RDF Schema Specification 1.0 published as a W3C Candidate Recommendation ( call for implementation)

• Aug 1999: RDF Interest Group created

• Feb 1999: RDF Model and Syntax Specification released as a W3C Recommendation (press release)

• May 1998 RDF - Using XML to describe Data, Swick, WWW8 presentation

• April 1998 WWW7 Tutorial, Using Web Metadata: Dublin Core and the Resource Description Framework, Lagoze, Miller, Lassila, Swick, Iannella, Schloss, Weibel

• Dec 1997 W3C Metadata Activity Statement presented to the W3C Membership

• Nov 1997 Introduction to RDF Metadata, W3C NOTE 1997-11-13, Ora Lassila

• Oct 1997 first RDF working draft released