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Resource Resource Description Description FrameworkFramework

Out of chaos, orderOut of chaos, order

Presentation by Ray James

For Semantic Web

UT Austin, Spring 2006

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RDF overview• What RDF is• What RDF can do• How to use RDF• Current RDF applications• RDF’s future• Summary & Sources

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RDF basics• Metadata is constructed

information• Metadata is developed by

people for a purpose or function

• Metadata can be a surrogateFrom Karen Coyle

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What RDF is• Key Definitions: Resource Description Framework: An XML

expression used to make simple assertions about relationships between things.

RDF Schema: A language used to describe the relationship between classes of things, or relationships between concepts in a particular domain.

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In other words• RDF defines a convention essential for

the Semantic Web• RDF is machine and human readable

but primarily for the machine• RDF is an infrastructure that enables

the encoding, exchange, and reuse of structured metadata.*

* Eric Miller

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What RDF is• History dates just over a decade• Creation process began in 1990s;

outgrowth of PICS • First RDF working draft October 1997• Semantic Web Activity & first RDF

Interest Group meeting, February 2001• Collaborative design process

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What RDF is• Breaking down RDF

– Anything can be a resource: Web page, PDA, document, etc. (identified with URI)

– Description means how a resource is related to any other resource or object

– Framework means ontological construct

Source: www.w3.org

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Describing RDFRDF promotes semantic interoperability; XML promotes syntactic interoperability.

Diagram from Dr. Miles Efron lecture notes.

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Describing RDF• RDF is all about the “triples”• Resource, Property, ValueOr• Subject, Predicate, Object

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RDF triples graphically

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More on RDF triples• An Object can become Subject of new

triple• ‘Nesting’ of properties without limit• Triples concept maintained in RDF

Schema• RDFS creates vocabularies• RDFS triples are: classes, class

properties and (atomic) values

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RDF graphically

From: Explorer’s Guide to the Semantic Web

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RDF in wordsThere is a person who is named William

Sparks who has a telephone number 435-555-6789 and who has an address which is composed of an address (number and street) and a city and a state and who has an e-mail account which was opened on Aug. 1, 2001 and uses the address wsparks@malto.com. Subject Predicate Object

Nested-subject Object

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ReificationReification describes the act of making a

data model for a previously abstract concept.

Reification allows a computer to process an abstraction as if it were any other data

From Wikipedia

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An RDF document

Adapted from http://www.ukoln.ac.uk/metadata/resources/dc/datamodel/WD-dc-rdf

<?xml version="1.0"?> <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc="http://dublincore.org/2003/03/24/dces"> <rdf:Description rdf:about="http://www.ukoln.ac.uk/metadata/resources/dc/datamodel/WD-dc-rdf/"> <dc:title> Guidance on expressing the Dublin Core within the Resource Description Framework (RDF) </dc:title><dc:creator> Eric Miller </dc:creator><dc:subject> Dublin Core; Resource Description Framework; RDF; eXtensible Markup Language; XML </dc:subject><dc:publisher> Dublin Core Metadata Initiative </dc:publisher><dc:contributor> Dublin Core Data Model Working Group </dc:contributor><dc:date> 1999-07-01 </dc:date><dc:format> text/html </dc:format><dc:language> en </dc:language></rdf:Description> </rdf:RDF>

Subject Predicate Object

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In wordsThere is a document declared in Dublin Core Schema

found at the Dublin Core namespace (& RDF etc) http://www.ukoln.ac.uk/metadata/resources/dc/datamodel/WD-dc-rdf/ which has the title Guidance on expressing the Dublin

Core within the Resource Description Framework (RDF) created by Eric Miller whose subject keywords are Dublin Core; Resource Description Framework; RDF; eXtensible Markup Language; XML published by Dublin Core Metadata Initiative contributed by Dublin Core Data Model Working Group on the date 1999-07-01 written in the format text/html and in the language en (English).

Subject Predicate Object

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How RDF works• All essential information is at: http://www.w3.org/RDF• Find RDF validator at the website: http://www.w3.org/RDF/Validator/

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RDF applications

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<!-- /Creative Commons License --> <!-- <rdf:RDF xmlns="http://web.resource.org/cc/"

xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"> <Work rdf:about=""> <dc:title>Metadata: Data with a Purpose</dc:title> <dc:date>2004</dc:date> <dc:description>A general discussion of document/resource metadata and some related uses.</dc:description> <dc:creator><Agent> <dc:title>Karen Coyle</dc:title> </Agent></dc:creator> <dc:rights><Agent> <dc:title>Karen Coyle</dc:title> </Agent></dc:rights> <dc:type rdf:resource="http://purl.org/dc/dcmitype/Text" /> <dc:source rdf:resource="http://www.kcoyle.net/meta_purpose.html"/> <license rdf:resource="http://creativecommons.org/licenses/by-nc-nd/2.0/" /> </Work> <License rdf:about="http://creativecommons.org/licenses/by-nc-nd/2.0/"> <permits rdf:resource="http://web.resource.org/cc/Reproduction" /> <permits rdf:resource="http://web.resource.org/cc/Distribution" /> <requires rdf:resource="http://web.resource.org/cc/Notice" /> <requires rdf:resource="http://web.resource.org/cc/Attribution" /> <prohibits rdf:resource="http://web.resource.org/cc/CommercialUse" /> </License> </rdf:RDF>

RDF document

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RDF applications•Mozilla: describes e-mail, news•RSS: describes blogs•Annotea: describes Web pages•Dublin Core: describes meta data•Webscripter: defines and fuses

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RDF(S) creation applications

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More on Altova site

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RDF’s Future• Growing acceptance by Web site

producers and users of metadata• Programs like SemanticWorks are

positive signs that standard is healthy• Acceptance means use; use means

continuing acceptance• Continued support (likely) from W3C

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RDF SummaryRDF …

…is about relationships.…brings interoperability.…is all about triples.

…can be found at http://www.w3.org/RDF

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Sources• http://www.w3.org/RDF• http://www.altova.com• http://www.mozilla.org/rdf/doc/• http://www-db.research.bell-labs.com/user/pfps/

publications/oil-ieee.pdf OIL: An Ontology Infrastructure (Fensel and others)• www.dlib.org/dlib/may98/miller/05miller.html An Introduction to the Resource Development

Framework (Miller)• Explorer’s Guide to the Semantic Web (Passin)• http://www.kcoyle.net/jal2_Metadata.html Understanding Metadata and Its Purpose (Coyle)

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Questions?