More RDF

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More RDF

• CS 431 20040310
• Carl Lagoze Cornell University

Acknowledgements Eric Miller Dieter Fensel
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RDF Data Model

• Directed labeled graphs
• Model elements
• Resource
• Property
• Value
• Statement
• Containers

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RDF meta-model

• RDF basic types
• rdfResource everything that can be identified
  (with a URI)
• rdfProperty specialization of a resource
  expressing a binary relation between two
  resources
• Rdftype predefined property to express that
  subject of property is considered to be an
  instance of that category or class defined by the
  value of the property
• rdfstatement a triple with properties
  rdfsubject, rdfpredicate, rdfobject
• An RDF statement is a triple consisting of a
  resource (subject), a property and a second
  resource (object)
• (s p o)
• Expressible also as binary relations
• P(S,O) e.g., Title(R, War Peace)

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Expressing Simple Binary Relations
(R1 P1 R2)
P1(R1, R2)
ltRDF xmlns http//www.w3.org/TR/WD-rdf-syntax
gt ltDescription about R1gt ltxP1
resourceR2/gt gt lt/Descriptiongt lt/RDFgt
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Expressing n-ary relations
(Carl Lagoze address 301 College Ave,
Ithaca, NY 14850)
(Carl Lagoze address 301 College Ave
Ithaca NY 14850)
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Another n-ary relation example
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Expressing Collection Primitives in Binary
Relations
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Reification Structure
Staff member 85740 said the weight of item 10245
is 2.4 units
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Reification XML
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RDF Schemas

• Declaration of vocabularies
• properties defined by a particular community
• characteristics of properties and/or constraints
  on corresponding values
• Provides substructure for inferences based on
  existing triples
• Schema language is an expression of basic RDF
  model
• Schema Type System - Basic Types
• Property, Class, SubClassOf, Domain, Range
• Minimal (but extensible) at this time
• Expressible in the RDF model and syntax

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Schema Vocabularies

• Enables communities to share machine readable
  tokens and locally define human readable labels.

dcCreator
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Relationships among vocabularies
dcCreator
marc100
msdirector
bibAuthor
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Relationships among vocabulary elements
URIR
msdirector
John Smith
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RDF Schema Specializing Properties

• rdfssubPropertyOf allows specialization of
  relations
• E.g., the property father is a subPropertyOf
  the property parent
• subProperty semantics

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Sub-Property Semantics
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Constraints on Properties

• Force objects to be of a certain type
• rdfsdomain
• Restricts the type of resources that may have a
  specific property
• rdfsrange
• Restricts the type of resources that may be the
  value of a specific property

range
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Inferences from Constraints
doris
betty
eve
alice
charles
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Inferences from Constraints
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Class Hierarchy

• rdfsClass
• Resources denoting a set of resources range of
  rdftype
• rdfssubClassOf
• Create class hierarchy

rdftype
rdftype
rdfsclass
rdfssubClassOf
rdftype
rdftype
rdfclass
rdfclass
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Sub-Class Inferencing
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Sub-class Inferencing Example
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Jena Toolkit

• Robust tools for building and manipulating RDF
  models
• HP Labs Bristol
• Capabilities
• Model construction
• XML and N3 parsing
• Model persistence (DB foundation)
• Model querying
• Ontology building
• Inferencing
• http//www.hpl.hp.com/semweb/jena2.htm

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IsaViz

• Visualizing and constructing RDF models
• http//www.w3.org/2001/11/IsaViz/