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Chapter 4 OWLOutlineThe OWL Family TreeA Brief History of OWL: SHOESlide 5A Brief History of OWL: OILA Brief History of OWL: DAML-ONTA Brief History of OWL: DAML+OILA Brief History of OWL: OWLSlide 10Requirements for Ontology LanguagesExpressive Power vs Efficient ReasoningKinds of Reasoning about KnowledgeUses for ReasoningReasoning Support for OWLRDFS’s Expressive Power LimitationsSlide 17Slide 18Combining OWL with RDF SchemaThree Species of OWLOWL FullOWL DLOWL LiteUpward Compatibility for OWL SpeciesOWL Compatibility with RDF SchemaSlide 26Slide 27OWL Syntactic VarietiesOWL XML/RDF Syntax: Headerowl:OntologyOWL ClassesOWL ClassesOWL PropertiesDatatype PropertiesOWL Object PropertiesInverse PropertiesEquivalent PropertiesProperty RestrictionsSlide 40owl:allValuesFromowl:hasValueowl:someValuesFromCardinality RestrictionsSlide 45Special PropertiesSpecial PropertiesBoolean CombinationsSlide 49Slide 50Nesting of Boolean OperatorsEnumerations with owl:oneOfDeclaring InstancesNo Unique-Names AssumptionDistinct ObjectsSlide 56Data Types in OWLVersioning InformationSlide 59Combination of FeaturesRestriction of Features in OWL DLSlide 62Slide 63Restriction of Features in OWL LiteInheritance in Class HierarchiesSlide 66African Wildlife Ontology: ClassesAfrican Wildlife: Schematic RepresentationAfrican Wildlife: PropertiesAfrican Wildlife: Plants and TreesAn African Wildlife: BranchesAfrican Wildlife: LeavesAfrican Wildlife: CarnivoresAfrican Wildlife: HerbivoresAfrican Wildlife: GiraffesAfrican Wildlife: LionsAfrican Wildlife: Tasty PlantsPrinter Ontology – Class HierarchyPrinter Ontology – Products and DevicesPrinter Ontology – HP ProductsPrinter Ontology – Printers & Personal PrintersHP LaserJet 1100se PrintersA Printer Ontology – PropertiesSlide 84OWL in OWLClasses of Classes (Metaclasses)Metaclasses – Thing and NothingSlide 88Class and Property EquivalencesClass DisjointnessEquality and InequalitySlide 92Union and Intersection of ClassesRestriction ClassesRestriction PropertiesRestriction PropertiesSlide 97PropertiesPropertiesSlide 100Slide 101Future Extensions of OWLModules and ImportsDefaultsClosed World AssumptionUnique Names AssumptionProcedural AttachmentsRules for Property ChainingOWL 1.1ConclusionsChapter 4OWL Based on slides from Grigoris Antoniou and Frank van HarmelenOutline1. A bit of history2. Basic Ideas of OWL 3. The OWL Language4. Examples5. The OWL Namespace6. Future ExtensionsJoint EU/US CommitteeDAMLOntoKnowledge+OthersThe OWL Family TreeFramesDescription LogicRDF/RDF(S)OILDAML-ONTDAML+OIL OWLW3CSHOELogic ProgrammingA Brief History of OWL: SHOESimple HTML Ontology ExtensionsSean Luke, Lee Spector, and David Rager, 1996SHOE allows World-Wide Web authors to annotate their pages with ontology-based knowledge about page contents. We present examples showing how the use of SHOE can support a new generation of knowledge-based search and knowledge discovery tools that operate on the World-Wide Web. Supported adding “semantic” tags defined in an ontology plus prolog-like rules to web pages.A Brief History of OWL: SHOE<META HTTP-EQUIV="Instance-Key" CONTENT="http://www.cs.umd.edu/~george"> <USE-ONTOLOGY "our-ontology" VERSION="1.0" PREFIX="our" URL="http://ont.org/our-ont.html"> …<CATEGORY "our.Person"><RELATION "our.firstName" TO="George"><RELATION "our.lastName" TO="Cook"><RELATION "our.marriedTo" TO="http://www.cs.umd.edu/~helena"><RELATION "our.employee" FROM="http://www.cs.umd.edu">A Brief History of OWL: OILDeveloped by group of (largely) European researchers (several from EU OntoKnowledge project)Based on frame-based languageStrong emphasis on formal rigour. Semantics in terms of Description LogicsRDFS based syntaxFramesDescription LogicsRDF/RDF(S)OILDAML-ONTDAML+OIL OWLA Brief History of OWL: DAML-ONTDeveloped by DARPA DAML Program. –Largely US based researchersExtended RDFS with constructors from OO and frame-based languagesRather weak semantic specification–Problems with machine interpretation–Problems with human interpretationFramesDescription LogicsRDF/RDF(S)OILDAML-ONTDAML+OIL OWLA Brief History of OWL: DAML+OILMerging of DAML-ONT and OIL Basically a DL with an RDFS-based syntax.Development was carried out by “Joint EU/US Committee on Agent Markup Languages”Extends (“DL subset” of) RDFSubmitted to W3C as basis for standardisation–Web-Ontology (WebOnt)Working Group formedFramesDescription LogicsRDF/RDF(S)OILDAML-ONTDAML+OIL OWLA Brief History of OWL: OWL W3C Recommendation (February 2004)Based largely on the March 2001 DAML+OIL specificationWell defined RDF/XML serializationsFormal semantics–First Order–Relationship with RDFComprehensive test cases for tools/implementationsGrowing industrial take up.FramesDescription LogicsRDF/RDF(S)OILDAML-ONTDAML+OIL OWLOutline1. A bit of history2. Basic Ideas of OWL 3. The OWL Language4. Examples5. The OWL Namespace6. Future ExtensionsRequirements for Ontology LanguagesOntology languages allow users to write explicit, formal conceptualizations of domain modelsThe main requirements are:–a well-defined syntax –efficient reasoning support –a formal semantics –sufficient expressive power –convenience of expressionExpressive Power vs Efficient ReasoningThere is always a tradeoff between expressive power and efficient reasoning supportThe richer the language is, the more inefficient the reasoning support becomesSometimes it crosses the noncomputability borderWe need a compromise:–A language supported by reasonably efficient reasoners –A language that can express large classes of ontologies and knowledge.Kinds of Reasoning about KnowledgeClass membership –If x is an instance of a class C, and C is a subclass of D, then we can infer that x is an instance of DEquivalence of classes –If class A is equivalent to class B, and class B is equivalent to class C, then A is equivalent to C, tooConsistency–X instance of classes A and B, but A and B are disjoint–This is an indication of an error in the ontologyClassification–Certain property-value pairs are a sufficient condition for membership in a class A; if an individual x satisfies such conditions, we can conclude that x must be an instance of AUses for Reasoning Reasoning support is important for–checking the consistency of the ontology and the knowledge–checking for unintended relationships between classes–automatically
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