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chapter8

# chapter8 - Knowledge Representation using First-Order Logic...

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C H A P T E R 8 H A S S A N K H O S R A V I S P R I N G 2 0 1 1 Knowledge Representation using First-Order Logic

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Outline What is First-Order Logic (FOL)? Syntax and semantics Using FOL Wumpus world in FOL Knowledge engineering in FOL Required Reading: All of Chapter 8
Pros and cons of propositional logic Propositional logic is declarative -programming languages lack general mechanism for deriving facing from other facts Update to data structure is domain specific Knowledge and inference are separate Propositional logic allows partial/disjunctive/negated information unlike most programming languages and databases Propositional logic is compositional : meaning of B 1,1 P 1,2 is derived from meaning of B 1,1 and of P 1,2 Meaning in propositional logic is context-independent unlike natural language, where meaning depends on context Look, here comes superman. Propositional logic has limited expressive power unlike natural language E.g., cannot say "pits cause breezes in adjacent squares“ except by writing one sentence for each square

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Wumpus World and propositional logic Find Pits in Wumpus world B x,y (P x,y+1 P x,y-1 P x+1,y P x-1,y ) (Breeze next to Pit) 16 rules Find Wumpus S x,y (W x,y+1 W x,y-1 W x+1,y W x-1,y ) (stench next to Wumpus) 16 rules At least one Wumpus in world W 1,1 W 1,2 W 4,4 (at least 1 Wumpus) 1 rule At most one Wumpus W 1,1 W 1,2 (155 RULES) Keep track of location L x,y FacingRight Forward L x+1,y
First-Order Logic Propositional logic assumes the world contains facts , First-order logic (like natural language) assumes the world contains Objects : people, houses, numbers, colors, baseball games, wars, … Relations : red, round, prime, brother of, bigger than, part of, comes between, … Functions : father of, best friend, one more than, plus, …

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Logics in General Ontological Commitment: What exists in the world TRUTH PL : facts hold or do not hold.
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