Part 4 Web Ontology Language: OWL

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Part 4. A Semantic Web Primer. 2. Address Outline. Essential Ideas of OWL The OWL LanguageExamplesThe OWL NamespaceFuture Extensions. Section 4. A Semantic Web Primer. 3. Prerequisites for Ontology Languages. Metaphysics dialects permit clients to compose unequivocal, formal conceptualizations of area modelsThe principle necessities are:a all around characterized grammar effective thinking backing a formal semantics suffic

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´╗┐Section 4 Web Ontology Language: OWL Grigoris Antoniou Frank van Harmelen A Semantic Web Primer

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Lecture Outline Basic Ideas of OWL The OWL Language Examples The OWL Namespace Future Extensions A Semantic Web Primer

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Requirements for Ontology Languages Ontology dialects permit clients to compose unequivocal, formal conceptualizations of space models The principle necessities are: an all around characterized grammar proficient thinking bolster a formal semantics adequate expressive influence comfort of expression A Semantic Web Primer

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Tradeoff between Expressive Power and Efficient Reasoning Support The wealthier the dialect is, the more wasteful the thinking support turns out to be Sometimes it crosses the outskirt of noncomputability We require a bargain: A dialect upheld by sensibly productive reasoners A dialect that can express vast classes of ontologies and information. A Semantic Web Primer

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Reasoning About Knowledge in Ontology Languages Class participation If x is an example of a class C, and C is a subclass of D, then we can gather that x is a case of D Equivalence of classes If class An is proportional to class B, and class B is identical to class C, then An is proportionate to C, too A Semantic Web Primer

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Reasoning About Knowledge in Ontology Languages (2) Consistency X case of classes An and B, however An and B are disjoint This means that a mistake in the metaphysics Classification C ertain property-estimation sets are an adequate condition for enrollment in a class A ; if an individual x fulfills such conditions, we can infer that x must be an occurrence of An A Semantic Web Primer

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Uses for Reasoning backing is essential for checking the consistency of the cosmology and the learning checking for unintended connections between classes consequently characterizing occasions in classes Checks like the previous ones are important for planning vast ontologies, where numerous writers are included incorporating and sharing ontologies from different sources A Semantic Web Primer

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Reasoning Support for OWL Semantics is an essential for thinking bolster Formal semantics and thinking backing are normally given by mapping a philosophy dialect to a known intelligent formalism utilizing mechanized reasoners that as of now exist for those formalisms OWL is (mostly) mapped on a depiction rationale, and makes utilization of reasoners, for example, FaCT and RACER Description rationales are a subset of predicate rationale for which proficient thinking backing is conceivable A Semantic Web Primer

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Limitations of the Expressive Power of RDF Schema Local extent of properties rdfs:range characterizes the scope of a property (e.g. eats) for all classes In RDF Schema we can't proclaim extend limitations that apply to a few classes just E.g. we can't state that bovines eat just plants, while different creatures may eat meat, too A Semantic Web Primer

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Limitations of the Expressive Power of RDF Schema (2) Disjointness of classes Sometimes we wish to state that classes are disjoint (e.g. male and female ) Boolean mixes of classes Sometimes we wish to fabricate new classes by joining different classes utilizing union, crossing point, and supplement E.g. individual is the disjoint union of the classes male and female A Semantic Web Primer

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Limitations of the Expressive Power of RDF Schema (3) Cardinality confinements E.g. a man has precisely two guardians, a course is educated by no less than one instructor Special attributes of properties Transitive property (like "more prominent than") Unique property (like "is mother of") A property is the converse of another property (like "eats" and "is eaten by") A Semantic Web Primer

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Combining OWL with RDF Schema Ideally, OWL would expand RDF Schema Consistent with the layered engineering of the Semantic Web But essentially amplifying RDF Schema would conflict with getting expressive power and effective thinking Combining RDF Schema with rationale prompts to wild computational properties A Semantic Web Primer

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Three Species of OWL W3C'sWeb Ontology Working Group characterized OWL as three diverse sublanguages: OWL Full OWL DL OWL Lite Each sublanguage intended for satisfying distinctive parts of necessities A Semantic Web Primer

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OWL Full It utilizes all the OWL dialects primitives It permits the mix of these primitives in subjective routes with RDF and RDF Schema OWL Full is completely upward-good with RDF, both grammatically and semantically OWL Full is powerful to the point that it is undecidable No entire (or productive) thinking bolster A Semantic Web Primer

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OWL DL OWL DL (Description Logic) is a sublanguage of OWL Full that limits utilization of the constructors from OWL and RDF Application of OWL's constructors' to each other is denied Therefore it compares to an all around contemplated portrayal rationale OWL DL licenses proficient thinking support But we lose full similarity with RDF: Not each RDF report is a legitimate OWL DL archive. Each legitimate OWL DL report is a lawful RDF record. A Semantic Web Primer

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OWL Lite A significantly advance confinement limits OWL DL to a subset of the dialect constructors E.g., OWL Lite prohibits listed classes, disjointness articulations, and self-assertive cardinality. The benefit of this is a dialect that is less demanding to get a handle on, for clients actualize, for device developers The drawback is limited expressivity A Semantic Web Primer

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Upward Compatibility between OWL Species Every legitimate OWL Lite philosophy is a lawful OWL DL metaphysics Every lawful OWL DL cosmology is a lawful OWL Full cosmology Every substantial OWL Lite decision is a legitimate OWL DL conclusion Every legitimate OWL DL determination is a legitimate OWL Full determination A Semantic Web Primer

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OWL Compatibility with RDF S chema All assortments of OWL utilize RDF for their linguistic structure Instances are announced as in RDF, utilizing RDF descriptions and writing data OWL constructors are specializations of their RDF partners A Semantic Web Primer

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OWL Compatibility with RDF S chema (2) Semantic Web configuration goes for descending similarity with comparing reuse of programming over the different layers The upside of full descending similarity for OWL is accomplished for OWL Full, at the cost of computational immovability A Semantic Web Primer

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Lecture Outline Basic Ideas of OWL The OWL Language Examples The OWL Namespace Future Extensions A Semantic Web Primer

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OWL Syntactic Varieties OWL expands on RDF and utilizations RDF's XML-based sentence structure Other syntactic structures for OWL have additionally been characterized: An option, more clear XML-based grammar A theoretical punctuation, that is a great deal more reduced and meaningful than the XML dialects A realistic linguistic structure in view of the traditions of UML A Semantic Web Primer

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OWL XML/RDF Syntax: Header <rdf:RDF xmlns:owl ="http://www.w3.org/2002/07/owl#" xmlns:rdf ="http://www.w3.org/1999/02/22-rdf- syntax-ns#" xmlns:rdfs="http://www.w3.org/2000/01/rdf- schema#" xmlns:xsd ="http://www.w3.org/2001/ XLMSchema#"> An OWL cosmology may begin with a gathering of affirmations for housekeeping purposes utilizing owl:Ontology component A Semantic Web Primer

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owl:Ontology <owl:Ontology rdf:about=""> <rdfs:comment>An case OWL philosophy </rdfs:comment> <owl:priorVersion rdf:resource="http://www.mydomain.org/uni-ns-old"/> <owl:imports rdf:resource="http://www.mydomain.org/persons"/> <rdfs:label>University Ontology</rdfs:label> </owl:Ontology> owl:imports is a transitive property A Semantic Web Primer

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Classes are characterized utilizing owl:Class is a subclass of rdfs:Class Disjointness is characterized utilizing owl:disjointWith <owl:Class rdf:about=" # associateProfessor"> <owl:disjointWith rdf:resource="#professor"/> <owl:disjointWith rdf:resource="#assistantProfessor"/> </owl:Class> A Semantic Web Primer

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Classes (2) owl:equivalentClass characterizes equality of classes <owl:Class rdf:ID="faculty"> <owl:equivalentClass rdf:resource= "#academicStaffMember"/> </owl:Class> owl:Thing is the most broad class, which contains everything owl:Nothing is the vacant class A Semantic Web Primer

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Properties In OWL there are two sorts of properties Object properties , which relate items to different articles E.g. is-TaughtBy, administers Data sort properties , which relate items to datatype values E.g. telephone, title, age, and so on. A Semantic Web Primer

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Datatype Properties OWL makes utilization of XML Schema information sorts, utilizing the layered engineering of the SW <owl:DatatypeProperty rdf:ID="age"> <rdfs:range rdf:resource= "http://www.w3.org/2001/XLMSchema #nonNegativeInteger"/> </owl:DatatypeProperty> A Semantic Web Primer

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Object Properties User-characterized information sorts <owl:ObjectProperty rdf:ID="isTaughtBy"> <owl:domain rdf:resource="#course"/> <owl:range rdf:resource= "#academicStaffMember"/> <rdfs:subPropertyOf rdf:resource="#involves"/> </owl:ObjectProperty> A Semantic Web Primer

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Inverse Properties <owl:ObjectProperty rdf:ID="teaches"> <rdfs:range rdf:resource="#course"/> <rdfs:domain rdf:resource= "#academicStaffMember"/> <owl:inverseOf rdf:resource="#isTaughtBy"/> </owl:ObjectProperty> A Semantic Web Primer

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Equivalent Properties owl:equivalentProperty <owl:ObjectProperty rdf:ID="lecturesIn"> <owl:equivalentProperty rdf:resource="#teach

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