Chapter 7:
Resource Description
Framework (RDF)
Service-Oriented Computing: Semantics, Processes, Agents
– Munindar P. Singh and Michael N. Huhns, Wiley, 2005
RDF
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Chapter 7
Provides a basis for knowledge
representation
Simple language to capture assertions
(statements), which help capture
knowledge, e.g., about resources
RDF puts together old KR ideas but
uses the Web to enhance their range
and avoid some longstanding problems
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
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Why RDF?
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XML
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Chapter 7
Gives us a document tree
Doesn’t identify the content represented by
a document
Enables multiple representations for the
same content
RDF expresses the content itself
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
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Resources and Literals
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RDF captures descriptions of resources
A resource is an object
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A literal is something simpler
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Chapter 7
Of which a description can be given
Identified via a URI
A value, e.g., string or integer
Cannot be given a description
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
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Statements or Triples
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RDF is based on a simple grammar
An RDF document is just a set of
statements or triples
Each statement consists of
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Chapter 7
Subject: a resource
Object: a resource or a literal
Predicate: a resource
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
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Rendering RDF
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RDF is not about the surface syntax but
the content it captures
In principle, RDF is not tied to XML,
which makes it verbose, but it is the
common syntax, which we will use
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Uses standard XML namespace syntax
Namespace defined by the RDF standard
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Chapter 7
Typically abbreviated rdf and rdfs
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
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Example (Using Dublin Core)
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Chapter 7
<?xml version='1.0' encoding='UTF-8'?>
<rdf:RDF
xmlns:rdf="http://www.w3.org/1999/02/22-rdfsyntax-ns#"
xmlns:dc="http://purl.org/dc/elements/1.1/">
<rdf:Description
rdf:about="http://www.wiley.com/SOC">
<dc:title>Service-Oriented Computing</dc:title>
<dc:creator>Munindar</dc:creator>
<dc:creator>Michael</dc:creator>
<dc:publisher>Wiley</dc:publisher>
</rdf:Description>
</rdf:RDF>
rdf:Description gathers statements about one subject
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
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N-Triples Notation
<http://www.wiley.com/SOC>
<http://purl.org/dc/elements/1.1/title>
"Service-Oriented Computing" .
<http://www.wiley.com/SOC>
<http://purl.org/dc/elements/1.1/creator>
"Munindar" .
<http://www.wiley.com/SOC>
<http://purl.org/dc/elements/1.1/creator>
"Michael" .
<http://www.wiley.com/SOC>
<http://purl.org/dc/elements/1.1/publisher>
"Wiley” .
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Chapter 7
Could also write individual statements in the XML syntax, but
the rdf:Description element simplifies the notation
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
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Collections
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Function as containers
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Accompanied by properties to extract
elements
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Chapter 7
rdf:Bag
rdf:Sequence
rdf:Alt
Schematically represented as rdf:_1, and
so on
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
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Reification of Statements
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Reify: to make referenceable
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Chapter 7
Needed to quote statements (e.g., to agree
or disagree with them); assert modalities
Make a statement into a resource; then
talk about it
rdf:Statement is the class whose rdf:type
the given statement (object) is; additional
properties such as rdf:subject, rdf:object,
and rdf:predicate
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
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RDF Schema
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Analogous to an object-oriented type
system built on top of RDF. Defines
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Chapter 7
rdfs:Class, rdfs:subClassOf
rdfs:Resource, rdfs:Literal
rdfs:Property, rdfs:subPropertyOf
rdfs:range, rdfs:domain
rdfs:label, rdfs:comment, rdfs:seeAlso
Applications of RDF Schema deferred to
OWL, which greatly enhances the above
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
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RDF Schema versus XML Schema
Both help define custom vocabularies
 An XML Schema document gives us
syntactic details
 An RDF Schema document gives us
meaning
 An OWL document (next chapter)
captures richer meaning
Chapter 7
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
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Chapter 7 Summary
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RDF captures the deep structure whereas
XML captures the surface structure
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RDF is based on an simple linguistic
representation: subject, predicate, object
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But “webified” via URIs
RDF comes with RDF Schema
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Chapter 7
RDF captures graphs in general
In essence, an object-oriented type system
Has been used for important custom vocabularies
For our purposes, best used as part of OWL
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