Knowledge Representation Guest Lecture - CSE 335/435IntroductionSemantic NetworksFrame SystemsDescription LogicDescription Logic InferenceOntologyCyc Upper OntologyThe Semantic WebA Web of OntologiesRDF and RDF SchemaURIs and NamespacesOWLOWL Class ConstructorsOWL AxiomsOWL RDF SyntaxOWL InferenceIs the Semantic Web a Fad?ConclusionFor more information...The EndEvolution of Web StandardsSpecies of OWLSemantic Web ChallengesKnowledge RepresentationGuest Lecture - CSE 335/435Jeff HeflinLehigh UniversityIntroductionWhat is knowledge representation (KR)?–subfield of artificial intelligence–concerns»storing general purpose information»discovering the consequences of that informationThere are many KR languages–each with its pros and consSemantic NetworksPenguinBirdTweetyTruecanFlyinstanceOfCanaryisaFalsecanFlyOpusinstanceOfisaFrame SystemscanFlynumLegsTrue2sings Trueisaweight 22instanceOfmovesBycoveringWingsFeathersBirdCanaryTweetyslotfillerDescription LogicFather ≡ And(Male,Parent)–a father is a male parentParent ≡ AtLeast(1, hasChild)–a parent has at least one childBand ⊑ All(members, Musician)–every member of a band is a musicianTrio ⊑ And(All(members, Musician), Exactly(3, members)) –a trio has exactly three members, all of whom are musiciansDescription Logic Inferencesubsumption–is one class a subclass of another?–calculate implicit isa relationsclassification–does an object belong to a class?–example»bobMale, bobParent»is bobFather true?OntologyDefinition–a logical theory that accounts for the intended meaning of a formal vocabulary (Guarino 98)–has a formal syntax and unambiguous semantics–inference algorithms can compute what logically followsStructure–specifies at least a taxonomy–often richer definitionsCyc Upper OntologyFrom http://www.cyc.com/cycdoc/vocab/upperont-diagram.htmlThe Semantic WebDefinition–The Semantic Web is not a separate Web but an extension of the current one, in which information is given well-defined meaning, better enabling computers and people to work in cooperation. (Berners-Lee et al., Scientific American, May 2001)Applications–managing corporate web sites (intranets)–more automatic generation of web portals–better indexing of multimedia resources–web agents and web services–ubiquitous computingA Web of OntologiesA1A2B3B1B2C1D1E1F1revisesrevises revisesextendsextendsextendsextendsextendsextends extendsS1S2S3S5S4commits tocommits tocommits tocommits tocommits tocommits toRDF and RDF Schemau:ChairJohn Smithrdf:typeg:name<rdf:RDF xmlns:g=“http://schema.org/gen” xmlns:u=“http://schema.org/univ”> <u:Chair rdf:ID=“john”> <g:name>John Smith</g:name> </u:Chair></rdf:RDF>g:Persong:namerdfs:Class rdf:Propertyrdf:typerdf:typerdf:typerdfs:subclassOfrdfs:domain<rdf:Property rdf:ID=“name”> <rdfs:domain rdf:resource=“Person”></rdf:Property><rdfs:Class rdf:ID=“Chair”> <rdfs:subclassOf rdf:resource= “http://schema.org/gen#Person”></rdfs:Class>URIs and NamespacesURI–Uniform Resource Identifier–includes URLs–but also anything that you can design an identification scheme for–helps to prevent collision of names–all the “symbols” in RDF are either URIs or LiteralsNamespace–a mechanism for abbreviating URIs–by assigning a prefix for a URI fragmentOWLWeb Ontology Language–W3C Recommendation–released Feb. 2004–based on RDF<rdf:Description rdf:about=“”> <imports resource=“www.books.com/bookont”><rdf:Description><Book rdf:ID=“book26489”><author>E.B. White</author><title>Charlotte’s Web</title><price>6.99</price><subject rdf:resource=“&bookont;FictionChild”></Book><Class ID=“Book”><Property ID=“subject”> <domain resource=“#Book”> <range resource=“#Topic”></Property><Class ID=“FictionChild”> <subclassOf resource=“#Fiction”> <subclassOf resource=“#Childrens”></Class>…importsbookont ontologymarkup linked to semanticssemantic markupOWL Class Constructorsborrowed from Ian HorrocksOWL Axiomsborrowed from Ian HorrocksOWL RDF Syntax<owl:Class rdf:ID=”Band”> <rdfs:subClassOf> <owl:Restriction> <owl:onProperty rdf:resource=”#hasMember” /> <owl:allValuesFrom resource=”#Musician” /> </owl:Restriction> </rdfs:subClassOf></owl:Class> A Band is a subset of the set of objects which only have Musicians as membersOWL InferenceBin Laden<owl:Property rdf:about=“&s;head”> <rdfs:subPropertyOf rdfs:resource=“&s;member” /></owl:Property><owl:Class rdf:about=“&t;Terrorist”> <owl:sameClassAs> <owl:Restriction> <owl:onProperty rdf:resource=“&s;member” /> <owl:someValuesFrom rdf:resource=“&s;TerroristOrg” /> </owl:Restriction> </owl:sameClassAs></owl:Class>Al Qaeda TerrorOrgTerroristtypeheadtypeThe head of an organization is also a member of itA member of a terror organization is a terroristTherefore, the head of a terror organization is a terroristIs the Semantic Web a Fad?Open source Semantic Web tools–from IBM, Hewlett-Packard, Nokia, etc.Commercial software vendors–Oracle 11g RDBMS supports RDF and much of OWL–Adobe’s products use RDF to provide metadata for documents, photos–Semantic Web specific companies: TopQuadrant, Aduna Software, etc.~65 million Semantic Web documents (as of October 2009)–Yahoo SearchMonkey uses RDF to present richer search results–Google now indexes RDFa (a means for embedding RDF in web pages)Semantic Web enabled sites–Data.gov: much of U.S. government’s open data is available in RDF–Newsweek: annotates articles with RDFa –BBC Music: exports RDF playlists, RDF for all artists–Harper’s Magazine: connects articles to events on a timeline–DBPedia: a Semantic Web version of WikipediaConclusionKR has a long and impressive historyThe Semantic Web is a direct descendant of KR researchThe Semantic Web is growing at an extraordinary rate–it has potential to revolutionize the Web!For more information...For more on the Semantic Web–http://www.cse.lehigh.edu/~heflin/–http://www.semwebcentral.org/–http://www.w3.org/2001/sw/–http://www.semanticweb.org/Contact me–[email protected] EndEvolution of Web StandardsXML<tr><td><b>Charlotte’s Web</b> -E.B. White, Garth Williams.<font color=“Red”>$6.99</font></td></tr><book><title>Charlotte’s