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Knowledge Interchange Format
Michael Gruninger
National Institute of Standards and Technology
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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