Rules & Ontologies OWL 2 RL & SWRL Description Logic ... - LPIS

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OWL Restrictions someValuesFromNon-expressible constructs• someValuesFrom(P,D)– the anonymous class of all x for which there existsat least one y instance of D, such that P(x, y).• someValuesFrom(P,D) subClassOf CP(X,Y), D(Y) → C(X)• The opposite direction cannot in general beexpressed.• Cardinality constraints and Complement ofclasses cannot be expressed in Horn logic inthe general case.4-21Rules & OntologiesA Semantic Web Primer, 3rd Edition4-22Rules & OntologiesA Semantic Web Primer, 3rd EditionOWL 2 RL – ConclusionsSemantic Web Rules Language(SWRL)• Allowed constructors allow usefulexpressivity for many practical cases• Guarantees correct interchange betweenOWL reasoners independent of CWA andUNA• Allows for translation into efficientlyimplementable reasoning techniques basedon databases and logic programs• A proposed Semantic Web languagecombining OWL 2 DL with function-free Hornlogic, written in Datalog RuleML• It allows Horn-like rules to be combined withOWL 2 DL ontologies.4-23Rules & OntologiesA Semantic Web Primer, 3rd Edition4-24Rules & OntologiesA Semantic Web Primer, 3rd Edition6
Rules in SWRLRule Heads4-25• B 1 , …,B n → A 1 , …,A m• commas denote conjunction on both sides ofthe arrow• A 1 , …,A m ,B 1 , …,B n can be– C(x), P(x, y), sameAs(x, y), differentFrom(x,y),– C is an OWL description, P is an OWL property,– x, y are Datalog variables, OWL individuals, orOWL data values.Rules & OntologiesA Semantic Web Primer, 3rd Edition4-26• If the head of a rule has more than one atomthe rule can be transformed to an equivalentset of rules with one atom in the head in astraightforward way– conjunction of atoms without shared variables• A(X,Y)→ B(X),C(Y)– A(X,Y)→ B(X)– A(X,Y)→ C(Y)Rules & OntologiesA Semantic Web Primer, 3rd EditionComplexity of SWRLSWRL vs. OWL 2 RL4-27• Arbitrary OWL expressions (e.g. restrictions),can appear in the head or body of a rule.• This adds significant expressive power toOWL, but at the high price of undecidability• There can be no inference engine that drawsexactly the same conclusions as the SWRLsemantics.Rules & OntologiesA Semantic Web Primer, 3rd Edition4-28• OWL 2 RL tries to combine the advantages of bothlanguages in their common sublanguage• SWRL takes a more maximalist approach and unitestheir respective expressivities.• The challenge is to identify sublanguages of SWRL thatfind the right balance between expressive power andcomputational tractability.– A candidate is the extension of OWL DL with DL-safe rules– Every variable must appear in a non-description logic atom in the rulebodyRules & OntologiesA Semantic Web Primer, 3rd Edition7
Page 1 and 2: Rules & OntologiesDescription Logic
Page 3 and 4: OWL 2 RLOWL 2 RL Advantages (1/2)
Page 5: More OWL ConstructsUnion (1)4-17•
Page 9 and 10: Example SWRL Rules:String Built-ins
Page 11: SWRLTabSWRLTab Wiki :http://protege
Page 14: 4-53Rule Markup Language (RuleML)

Rules & Ontologies OWL 2 RL & SWRL Description Logic ... - LPIS

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