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Knowledge Interchange Format Michael Gruninger National Institute of Standards and Technology gruning@cme.nist.gov
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What is KIF? Knowledge Interchange Format (KIF) is a language designed for use in the interchange of knowledge among disparate computer systems
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What is Knowledge? Facts –William is the brother of Harold. –Charles is not the brother of George. Statements/Rules/Constraints –The mother of Charles is either Elizabeth or Ann. –Two people are siblings if and only if they are brother or sister. –Every person has a mother.
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How Will KIF be Used? Specification of ontologies –Standard Upper Ontology –Process Specification Language –Semantic Web Software agent communication Automated deduction and constraint satisfaction
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Features of KIF The language has a declarative semantics. The language is logically comprehensive. The language provides for the representation of knowledge about knowledge.
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Organization of KIF Part 1 (KIF-Core) : syntax and semantics of a language equivalent to first-order logic. Part 2 (Sorted KIF) specifies the syntax and semantics for class hierarchies. Part 3 (MetaKIF) syntax and semantics of the metatheory of KIF-Core.
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Scope of KIF Core Language of first-order logic: Language with logical symbols for –connectives (conjunction, disjunction, negation, implication, equivalence), –equality, –quantifiers (existential and universal)
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Example KIF Sentences The mother of Charles is either Elizabeth or Ann. (forall (?x) (=>(mother Charles ?x) (or (= ?x Elizabeth) (= ?x Ann)))) Everyone’s age must be greater than 0. (forall (?x) (greater (age ?x) 0))
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Example KIF Sentences Nobody can be both a brother and a sister. (forall (?x ?y) (=>(bother ?x ?y) (not (sister ?x ?y)))) Every person has a mother. (forall (?x) (=> (person ?x) (exists (?y) (and(person ?y) (mother ?x ?y)))))
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Example KIF Sentences Two people are siblings if and only if they are brother or sister. (forall (?x ?y) (=>(and(person ?x) (person ?y)) ( (sibling ?x ?y) (or(brother ?x ?y) (sister ?x ?y)))))
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Semantics: Intuitions A universe of discourse is the set of all objects within some domain. Terms are used to denote objects in the universe. For every set of objects, a function associates a unique object in the universe. For every set of objects, a relation associates a truth value.
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Semantics: Structures A structure consists of a nonempty set O together with the functions: – Interpretation function –Semantic valuation function –Satisfaction function
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Semantics: Models A structure satisfies a sentence if and only if ( ) = true A structure is a model of a theory T if and only if it satisfies each sentence in T A theory T entails a sentence if and only if every model of T satisfies .
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Inference A proof system consists of a set of KIF sentences and a set of inference rules that transform sentences into new ones. A sentence is provable from a theory T if and only if can be generated by applying a finite number of inference rules to the sentences of T.
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Compliance A proof system is compliant with KIF if and only if: –It is sound -- every sentence that is provable from a theory is entailed by the theory. –It is complete -- every sentence that is entailed by a theory is provable from the theory.
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Additional Features KIF-Core also allows quantification over relations and functions that are denoted by words in the lexicon of a theory. (forall (?r ?x ?y) ( (symmetric ?r) ( (?r ?x ?y) (?r ?y ?x))))
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Next Steps Incorporation of namespaces for KIF modules Semantics for sequence variables Syntax and semantics for Sorted-KIF Syntax and semantics for MetaKIF
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