Factors influencing Forward and Backward chaining Is the goal - PowerPoint PPT Presentation

Factors influencing Forward and Backward chaining • Is the goal precisely known? • Fan-in and Fan-out of rules.

Rule Structure R 1 : P 1 ^ P 2 ^ P 3 ^ . . . . . . ^ Pn Q 1 R 2 : P 1 ^ P 2 ^ P 3 ^ . . . . . . ^ Pn Q 2 . R k : P 1 ^ P 2 ^ P 3 ^ . . . . . . ^ Pn Q k P 1 P 2 . Pn AND OR Q 1 Q 2 . Q k

Forward chaining P 1 P 2 .. Pn Q 1 AND AND Mk P 1 M2 Q 1 P 2 M1 P k • If Fan-out is less Forward chaining is preferable ?

Important Data structure: AND-OR Graph S AND D OR A OR B C D n D 3 A 1 A 2 A 3 D 1 D 2 A n B 1 B 2 B 3 C 2 C 1 • Structure of AND-OR Graph decides the direction of inferencing.