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RDF and OWL
 

RDF and OWL

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A simple overview of the building blocks of the Semantic Web. I created this to present to the Semantic Web Affinity Group at Razorfish.

A simple overview of the building blocks of the Semantic Web. I created this to present to the Semantic Web Affinity Group at Razorfish.

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    RDF and OWL RDF and OWL Presentation Transcript

    • RDF & OWL A simple overview of the b uilding blocks of the Semantic Web Presented by Rachel Lovinger Semantic Web Affinity Group December 2007
    • RDF = Resource Description Framework
      • Purpose: To provide a structure (aka framework) for describing identified things (aka resources)
      RDF
      • Identified ?
      • In order to make meaningful statements in RDF, the thing you’re talking about has to be identified in some unique way.
      • http://www.foaf.com/Person#RachelLovinger
      • http://www.allmovie.com/Actor#WillSmith
      • URIs (uniform resource identifiers) look like URLs, but they may not represent an actual web page.
      RDF
      • Composed of three basic elements
      • Resources – the things being described
      • Properties – the relationships between things
      • Classes – the buckets used to group the things
      RDF
      • The elements are combined to make simple statements in the form of Triples
      • <Subject> <Predicate> <Object>
      • Men In Black stars Will Smith
      • <MenInBlack> <hasStar> <WillSmith>
      RDF
      • Information Expressed in Triples
      • <http://www.w3.org/2001/sw/RDFCore/ntriples/> <dc:creator> &quot;Dave Beckett&quot; .
      • <http://www.w3.org/2001/sw/RDFCore/ntriples/> <dc:creator> &quot;Art Barstow&quot; .
      • <http://www.w3.org/2001/sw/RDFCore/ntriples/> <dc:publisher> <http://www.w3.org/> .
      • Can also be expressed as XML
      • <rdf:RDF xmlns:rdf=&quot;http://www.w3.org/1999/02/22-rdf-syntax-ns#&quot; xmlns:dc=&quot;http://purl.org/dc/elements/1.1/&quot;>
      • <rdf:Description rdf:about=&quot;http://www.w3.org/2001/sw/RDFCore/ntriples/&quot;> <dc:creator>Art Barstow</dc:creator>
      • <dc:creator>Dave Beckett</dc:creator>
      • <dc:publisher rdf:resource=&quot;http://www.w3.org/&quot;/>
      • </rdf:Description>
      • </rdf:RDF>
      RDF
      • RDF Properties
      • type
      • subClassOf
      • subPropertyOf
      • range
      • domain
      • label
      • comment
      RDF
      • type – a resource belongs to a certain class
      • <WillSmith> <type> <Actor>
      • This defines which properties will be relevant to Will Smith.
      RDF
      • subClassOf – a class belongs to a parent class
      • <Actor> <subClassOf> <Person>
      • This means that all members of the actor class are also members of the Person class. All properties are inherited, and new properties specific to Actor can be added.
      • <WillSmith> <type> <Actor>
      • implies <WillSmith> <type> <Person>
      RDF
      • subPropertyOf – a property has a parent property
      • <hasStar> <subPropertyOf> <hasActor>
      • This means that, if you make a statement using the hasStar property, a more general statement using the hasActor property is also true.
      • <MenInBlack> <hasStar> <WillSmith>
      • implies <MenInBlack> <hasActor> <WillSmith>
      RDF
      • range & domain – the types of resources that use a property
      • <hasStar> <range> <Actor>
      • <hasStar> <domain> <Movie>
      • This means that, if you make a statement using the hasStar property, the system will assume that the subject is a Movie and the object is an Actor.
      • <WillSmith> <hasStar> <MenInBlack>
      • is an untrue statement, but not invalid
      RDF
      • label – a human-readable name for a resource
      • <http://www.allmovie.com/Actor#WillSmith> <label> <Will Smith>
      RDF
      • comment – a human-readable description
      • <https://aarfwiki.main.corp/wiki/index.php/File:RDF_OWL.pdf> <comment> <A presentation that Rachel gave at the December 2007 Semantic Web Affinity Group Meeting>
      RDF
    • RDF Blackberry Fruit typeOf BerryPie EdibleThing typeOf subClassOf ingredientOf Blackberry
      • Why is RDF uniquely suited to expressing data and data relationships?
      • More flexible – data relationships can be explored from all angles
      • More efficient – large scale, data can be read more quickly
        • not linear like a traditional database
        • not hierarchical like XML
      RDF
    • Namespaces
      • A method for qualifying names used in an XML document. Can be used to indicate usage of a standard, or to specify a unique version of the term.
      • dc:creator
      • rdf:type
      • foaf:Person
      • foaf:knows
      • aarf:Employee
      Namespaces
    • OWL = Web Ontology Language
    • OWL
      • Purpose: To develop ontologies that are compatible with the World Wide Web.
      OWL
      • Ontologies ?
      • Definition and classification of concepts and entities, and the relationships between them.
      OWL
      • Based on the basic elements of RDF; adds more vocabulary for describing properties and classes.
      • Relationships between classes (ex: disjointWith)
      • Equality (ex: sameAs)
      • Richer properties (ex: symmetrical)
      • Class property restrictions (ex: allValuesFrom)
      OWL
      • Relationships between Classes
      • disjointWith – resources belonging to one class cannot belong to the other
      • <Person> <disjointWith> <Country>
      • complementOf – the members of one class are all the resources that do not belong to the other
      • <InanimateThings> <complementOf> <LivingThings>
      OWL
      • Equality
      • sameAs – indicates that two resources actually refer to the same real-world thing or concept
      • <wills> <sameAs> <wismith>
      • equivalentClass – indicates that two classes have the same set of members
      • <CoopBoardMembers> <equivalentClass> <CoopResidents>
      OWL
      • Richer Properties
      • Symmetric – a relationship between A and B is also true between B and A
      • <WillSmith> <marriedTo> <JadaPinkettSmith>
      • implies <JadaPinkettSmith> <marriedTo> <WillSmith>
      • Transitive – a relationship between A and B and between B and C is also true between A and C
      • <piston> <isPartOf> <engine>
      • <engine> <isPartOf> <automobile>
      • implies <piston> <isPartOf> <automobile>
      OWL
      • Richer Properties continued
      • inverseOf – a relationship of type X between A and B implies a relationship of type Y between B and A
      • <starsIn> <inverseOf> <hasStar>
      • <MenInBlack> <hasStar> <WillSmith>
      • implies <WillSmith> <starsIn> <MenInBlack>
      OWL
      • Class Property Restrictions – define the members of a class based on their properties
      • allValuesFrom – resources with properties that only have values that meet this criteria
        • Example: Property: hasParents, allValuesFrom: Human
        • Resources that meet this criteria can be defined as also being members of the Human class
      • someValuesFrom – resources with properties that have at least one value that meets criteria
        • Example: Property: hasGraduated, someValuesFrom: College
        • Resources that meet this criteria can be defined as being members of the CollegeGraduates class
      OWL
      • This seems complicated. Why do it?
      • These capabilities allows systems to express and make sense of first order logic.
      • All men are mortal
      • Socrates is a man
      • Therefore, Socrates is mortal
      OWL
      • Inferences
      • Create new triples based on existing triples
      • Deduce new facts based on the stated facts
      • <piston> <isPartOf> <engine>
      • <engine> <isPartOf> <automobile>
      • implies <piston> <isPartOf> <automobile>
      OWL
      • Three Flavors of OWL
      • OWL Lite – uses a subset of the capabilities
      • OWL DL – uses all the capabilities, but some are used in restricted ways
      • OWL Full – unrestricted use of capabilities; no guarantee that all resulting statements are valid
      OWL
    • SKOS = Simple Knowledge Organization System
      • Also based on RDF
      • Designed specifically to express information that’s more hierarchical – broader terms, narrower terms, preferred terms and other thesaurus-like relationships
      • Extendable into OWL, if needed
      SKOS
    • Need more?
      • SchemaWeb: http://www.schemaweb.info/default.aspx
      • RDF Primer: http://www.w3.org/TR/REC-rdf-syntax/
      • OWL / Semantic Web: http://www.w3.org/2004/OWL/
      • SKOS: http://www.w3.org/2004/02/skos/
      • Dublin Core: http://dublincore.org/
      • Namespaces: http://www.w3.org/TR/REC-xml-names/
      • URIs: http://www.w3.org/Addressing/
      Resources