L2knowledge(ch2)

L2knowledge(ch2) - KNOWLEDGE REPRESENTATION AND INFERENCE...

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cse 352 Lecture Notes (2) Professor Anita Wasilewska KNOWLEDGE REPRESENTATION AND INFERENCE CHAPTER 2 (AI book)
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Requirements for Knowledge Representation Languages • Representational adequacy: It should allow to represent all knowledge that one needs to reason with. • Inferential Adequacy: It should allow new knowledge to be inferred from basic set of facts.
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Requirements for Knowledge Representation Languages • Inferential Efficiency: Inferences should be made efficiently. • Naturalness: The language should be reasonably natural and easy to use.
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Requirements for Knowledge Representation Languages • Clear Syntax and Semantics: We should clearly define • the language, • allowable formulas, • and their meaning.
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Syntax and Semantics • Syntax (Symbols): Formal Language = Set of Symbols. • Semantics: semantics is the assignment of well defined meaning to all symbols
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Syntax and Semantics (Cont.) • Example 1: Propositional Logic Knowledge representation: Syntax: propositional language – p q – p and q represent logical sentences.
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Syntax and Semantics Example 1 − Classical Propositional Logic Semantics: If light goes on, then bring a towel. p : light goes on, q: bring a towel p is True or False. q is True or False. T F T T F F T T
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Syntax and Semantics • We say: A is TTrue (tautologically true) iff A • (A is a propositional tautology) • Example: (A B ) = TTrue iff (p q )
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Syntax and Semantics • Example 2 for Syntax and Semantics: Syntax: (p q) p: 2+2 = 4 q: 2+7=3 (T F ) = F Hence, (p q) is False in this particular case.
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Syntax and Semantics (First Order Logic)
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