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Ontology Language Comparisons. doug foxvog 16 September 2004. Overview. Numerous Ontology Languages Different Logical Formalisms Syntactical Form Language Features. Numerous Ontology Languages. Most Computer Science fields have a few standard languages
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Ontology Language Comparisons doug foxvog 16 September 2004
Overview • Numerous Ontology Languages • Different Logical Formalisms • Syntactical Form • Language Features
Numerous Ontology Languages • Most Computer Science fields have a few standard languages • Ontologies expressed in many languages • Some languages merely for expression • Other languages for reasoning • Concentrate on reasoning
Term Hierarchies • Taxonomy – Broader/Narrower Term • OpenDirectory – 590,000 categories • Subclass Hierarchy • UNSPSC – 10,000 product types • Multiple Hierarchies (via different predicates) • WordNet – 152,000 synsets • Hierarchies + Logical Languages • Express Semantics • Considered Ontologies • Topic of Talk
RDF-S OWL OWL-Full OWL-DL OWL-Lite WSML DAML+OIL SHOE SWRL … KIF CycL PowerLoom FLORA-2 TRIPLE OntoBroker (OXML) Languages
Logical Formalisms • Description Logic: Roles, Classes, Individuals • Propositional Calculus: ∨ ∧ ¬ Variables • Subset without ¬ • Subset without ∨ • Subset without Variables • Horn Clauses only • First-Order Logic: $ • Higher-Order Logics • Quantification over predicates • Quantification over sets • Cardinality: ThereExistExactly, ThereExistAtLeast, ThereExistAtMost • Predicates as arguments
Ontology Logic Types • Restricted Description Logic • OWL-Lite, RDF-S, SHOE • Description Logic • OWL-DL, DAML+OIL, SWRL(+) • First-Order Logic • F-Logic, FLORA, OntoBroker, OWL-Full, TRIPLE • Extended First-Order Logic • Power-LOOM • Higher-Order Logic • CycL, KIF • Three-valued Logic • Power-LOOM
Propositional Calculus • Includes: ∨ ∧ ¬ Variables • Limitations for Computational Tractability • Subset without ¬ • Owl-Lite, RDF-S, SHOE • Subset without ∨ • OWL-Lite, RDF-S, OntoBroker • Subset without Variables • DAML+OIL, OWL, RDF-S • Horn Clauses only: (A ∧ B ∧ … ∧ C -> D) • SHOE
Closed World & Unique Name Assumptions • Closed World Assumption – If it cannot be proved true, it is false. • In: TRIPLE • Optional settings: CycL, FLORA, KIF, PowerLoom • Unique Name Assumption – Two things with different names are different. • In: PowerLoom, Ontobroker (not external term) • Default: TRIPLE • Optional: CycL
Syntax • LISP • CycL, KIF, PowerLoom • PROLOG Extensions • F-Logic, FLORA, TRIPLE • XML • DAML+OIL, OWL-Full, RDF-S, SHOE, SWRL • Multiple • OntoBroker, OWL-DL, OWL-Lite, WSML-Core
Ontology Language Components • Named Terms • Class / Type / Concept / Category … • Individual / Instance • Relation / Predicate / Role / Attribute / … • Reserved Operators; Special Symbols • Variables • Datatype Instances • Strings – Characters • Numbers – URIs, Dates, … • Data Structures • Sets – Lists • Statements
Variables and Quantifiers • Variables Imply Quantification • Default to forAll in statement • Default to either forAll or thereExists in Query • Most Ontological Languages Include Variables • Not in: DAML+OIL, OWL, RDF-S • Existential Quantification • Not in: FLORA-2, WSML-Core • Anonymous/ Don’t-Care Variables Effectively Provide Existential Quantification • In: CycL, FLORA-2 • Qualified Number Restrictions (Cardinality) • In: CycL, DAML+OIL, F-Logic, Ontobroker, OWL*, Power-LOOM, SWRL
Class – Type – Category Concept – Collection Multiple Inheritance – All Class/Individual Distinction Not: KIF, F-Logic, TRIPLE Metaclasses Disallowed: OWL, DAML+OIL, SWRL Code support: CycL Class as argument Not: OWL-DL, OWL-LITE, DAML+OIL, SWRL Class & Role with Same Name OWL*, F-Logic, TRIPLE Disjoint Classes Not RDF-S, SHOE, WSML
Relations – Predicates Roles – Properties – Attributes Relation – Predicate or Function Predicate Specifies interrelationship among meanings of terms. Value, when applied to arguments, is a truth value Binary Predicate – Two argument predicate Role/Property/Attribute Binary predicate applicable only to elements of a class Functional Predicate Predicate with single arg-n valid for other args fixed Functional Role/Property/Attribute Role with single arg2 valid for given arg1 Function Relation whose value when applied is that of corresponding functional argument stripped from Functional Predicate
Relations • Argument Type Constraints • Not in: OWL-Lite, KIF • For Attributes only: OWL-DL, OWL-Full • Inter-argument Restrictions • In: OWL-Full, OWL-DL, CycL, F-Logic, FLORA, WSML • Higher Arity Relations • In: FLORA-2, CycL, KIF, PowerLoom, SHOE, Ontobroker, TRIPLE (functions only) • Variable Arity Relations • KIF, CycL, Triple (functions only)
Relations • Transitive Binary Relations • DAML+OIL, CycL, FLORA (Transitive Closure), WSML, PowerLoom, SWRL, OWL, Ontobroker • Symmetric Binary Relations • CycL, FLORA, WSML, PowerLoom, SWRL, OWL, Ontobroker • Inverse Binary Relations • WSML, PowerLoom, SWRL, OWL, KIF, Ontobroker • Subrelations • By rule: KIF, TRIPLE
Attributes • Attribute Definition is Part of Class Definition • Range Includes: • individuals • datatype instances • Range Excludes • Relations • Classes • Statements • Languages with Attributes also Limit other Relations’ Arguments • OWL, DAML+OIL, RDF-S, WSML-Core
Functions & Functional Relations • Functions, but no Functional Predicates • FLORA, TRIPLE • Functional Predicates, but no Functions • OWL, Ontobroker • Neither Functions nor Functional Predicates • RDF-S, WSML-Core, SHOE • Functions and Functional Predicates • CycL, PowerLOOM, KIF, DAML+OIL, SWRL
Relation Features • Multiple Argument Constraints • RDF-S, OWL-Full, OWL-DL, DAML+OIL, CycL, TRIPLE, RDF-S (Constraint Disjunction!), WSML-Core • Default Argument Values • FLORA, Ontobroker, CycL • By rule: KIF, TRIPLE • Argument Cardinality Restrictions • OWL*, DAML+OIL, F-Logic, CycL, SWRL, Ontobroker, PowerLOOM
Rules – Axioms • Implication • Not: DAML+OIL, OWL, RDF-S • Rule/Formula as Object • WSML-Core, TRIPLE, FLORA, CycL, Ontobroker • Rule Exceptions • KIF, FLORA, CycL
Equality • Not • Not in: WSML-Core, SHOE, RDF-S, OWL-Lite • restricted: DAML+OIL (complimentOf) • Different • OWL, CycL, • Individual: DAML+OIL • Datatype Values: SHOE, SWRL • Classes: SHOE • Equals • Levels of Equality: CycL, FLORA • DAML+OIL (property, individual, class), TRIPLE, SHOE (datatype, class), SWRL (datatype, URI)
Datatypes & Sets Datatype Support • Arithmetic operations • String operations (concatenate, replace, …) • Comparisons • Extent of Support Often not Described Extensional Sets • OWL-FULL, OWL-DL, RDF-S, DAML+OIL, CycL, PowerLoom, KIF • Expressible: TRIPLE
Multiple Ontologies External Ontologies • Import External Ontologies • OWL,RDF-S, DAML+OIL, WSML, TRIPLE, SHOE • Specify Synonymous Term in External Ontology • CycL, Ontobroker Different Logical Worlds (Context/ Module/ Model/ Microtheory) in which to Reason • Hierarchy of contexts • FLORA, TRIPLE, PowerLOOM, CycL