RDF: The Resource Description Framework Machine Understandable Metadata for the Web Ralph R. Swick [email protected] W3C/MIT 2-November-1998
Mar 27, 2015
RDF:The Resource Description Framework
Machine Understandable Metadata for the Web
Ralph R. [email protected]
W3C/MIT2-November-1998
2-Nov-1998/swick 2
Introducing: RDF
• Improve on PICS, HTML, and XML
• Machine understandable metadata
• Support structured values
• Support metadata bureaus
• Encourage authenticated metadata
• Base for a variety of descriptions:– cataloging, privacy, accessibility, IPR, ...
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RDF Components
• Formal data model
• Syntax for interchange of data
• Schema Type system (schema model)
• Syntax for machine-understandable schemas
• Query and profile protocols
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RDF Data Model
• Imposes structural constraints on the expression of application data models– for consistent encoding, exchange and
processing of metadata
• Enables resource description communities to define their own semantics
• Provides for structural interoperability
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RDF Data Model
• Directed labeled graphs
• Model elements– Resource– Property– Property value– Statement
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RDF Model Primitives
Resource Value
Property
Statement
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RDF Model Example
page.html
John Smith
John’s Home Page
Creator
Title
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Structured Value
page.html
John’s Home Page
Title
Creator
John Smith [email protected]
Name Email
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RDF Syntax
• Uses eXtensible Markup Language (XML)
• Highly formalized– graph serialization
• Property Names and Values are always unambiguous
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Basic Example
page.html
John Smith
John’s Home Page
DC:Creator
DC:Title
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Basic RDF Example
<?xml version=“1.0”?><rdf:RDF
xmlns:rdf=“http://www.w3.org/TR/WD-rdf-syntax#”xmlns:dc=“http://purl.org/metadata/dublin_core#”>
<rdf:Description about=“page.html”> <dc:Creator>John Smith</dc:Creator> <dc:Title>John’s Home Page</dc:Title> </rdf:Description>
</rdf:RDF>
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Structured Value Example
page.html
John SmithJohn’s Home Page [email protected]
dc:Title
dc:Creator
Name Email
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Structured Value Example - 1
<?xml version=“1.0”?>
<RDFxmlns=“http://www.w3.org/TR/WD-rdf-syntax#”xmlns:dc=“http://purl.org/metadata/dublin_core#”xmlns:corp=“http://mycorp.com/corpSchema/”>
. . .
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Structured Value Example - 2. . .
<Description about=“page.html”> <dc:Creator> <Description> <corp:Name>John Smith</corp:Name> <corp:Email>[email protected]</corp:Email> </Description> </dc:Creator> <dc:Title>John’s Home Page</dc:Title></Description>
</RDF>
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Abbreviations: 1<rdf:RDF>
<rdf:Description about=“page.html”> <dc:Creator> <rdf:Description corp:Name=“John Smith” corp:Email=“[email protected]” /> </dc:Creator> <dc:Title>John’s Home Page</dc:Title></rdf:Description>
</rdf:RDF>
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Abbreviations: 2<rdf:RDF>
<rdf:Description about=“page.html”> <dc:Creator corp:Name=“John Smith” corp:Email=“[email protected]” /> <dc:Title>John’s Home Page</dc:Title></rdf:Description>
</rdf:RDF>
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Meta-description
page.htmlCost
$0.15
18-Apr-1999
ValidUntil
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Property Reification
page.htmlCost
$0.15
18-Apr-1999
ValidUntil
ObjectSubject
type
StatementCost
Predicate
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Meta-description Example - 1
<?xml version=“1.0”?>
<RDFxmlns:rdf =“http://www.w3.org/TR/WD-rdf-syntax#”xmlns:corp =“http://mycorp.com/schema/”>
. . .
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Meta-description Example - 2
. . .<rdf:Description about=“page.html” bagID=“D_001”> <corp:Cost>$0.15</corp:Cost></rdf:Description>
<rdf:Description aboutEach=“#D_001”> <corp:ValidUntil>18-Apr-1999</corp:ValidUntil></rdf:Description>
</rdf:RDF>
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Meta-description Example - 3
<rdf:RDF>
<rdf:Description about=“page.html” bagID=“D_001” corp:Cost=“$0.15”/>
<rdf:Description aboutEach=“#D_001” corp:ValidUntil=“18-Apr-1999”/>
</rdf:RDF>
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Summary
• 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• Signed RDF is the basis for trust
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For More Information...
The RDF Model and Syntax specification:
http://www.w3.org/TR/WD-rdf-syntax
RDF Schema Working Draft:
http://www.w3.org/TR/WD-rdf-schema
General information about RDF:
http://www.w3.org/RDF