CNF_Horn 1 - – e.g p – A special clause The empty clause shown as or • A formula is said to be in Conjunctive Normal Form(CNF if it is the

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Conjunctive Normal Form & Horn Clauses York University CSE 3401 Vida Movahedi York University- CSE 3401- V. Movahedi 1 02-CNF & Horn
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Overview Definition of literals, clauses, and CNF Conversion to CNF- Propositional logic Representation of clauses in logic programming Horn clauses and Programs Facts Rules Queries (goals) Conversion to CNF- Predicate logic [ref.: Clocksin- Chap. 10 and Nilsson- Chap. 2] York University- CSE 3401 2 02-CNF & Horn
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Conjunctive Normal Form A literal is either an atomic formula (called a positive literal) or a negated atomic formula (called a negated literal) e.g. p, ¬q A clause is A literal, or Disjunction of two or more literals, or
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Unformatted text preview: – e.g. p, – A special clause: The empty clause, shown as □ , :- or {} • A formula is said to be in Conjunctive Normal Form (CNF) if it is the conjunction of some number of clauses York University- CSE 3401 3 r q p 02-CNF & Horn CNF (example) York University- CSE 3401 4 ) ( ) ( ) ( t r r s q q p ˄ ˅ p q ˅ q ¬s r ˅ ¬r t 02-CNF & Horn CNF- Facts • For every formula of propositional logic, there exists a formula A in CNF such that A is a tautology • A polynomial algorithm exists for converting to A • For practical purposes, we use CNFs in Logic Programming York University- CSE 3401 5 02-CNF & Horn...
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This note was uploaded on 02/14/2012 for the course CSE 3401 taught by Professor Movahedi during the Fall '11 term at York University.

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CNF_Horn 1 - – e.g p – A special clause The empty clause shown as or • A formula is said to be in Conjunctive Normal Form(CNF if it is the

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