L5rulebasedsystems2(ch2)

L5rulebasedsystems2(ch2) - Production Systems ES (2) (Book...

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Production Systems ES (2) (Book and Busse book handout) CSE 352 Lecture Notes (5) Professor Anita Wasilewska
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Forward Chaining Data -> Rules -> Goal Also called DATA DRIVEN, BOTTOM UP, or ANTECEDENT chaining During the SELECTION step of each cycle, the RI is looking for applicable rules by MATCHING (unifying) condition part of a rule with the CURRENT CONTENT of the DB; Forward chaining is applied, i.e. the proper rule is FIRED and a new FACT (action part) is added to the DB. Process TERMINATES when the GOAL is reached , or when all possible FACTS are already inferred from the INITIAL database.
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Backward Chaining Also called GOAL-DRIVEN consequent chaining - The production system ESTABLISHES whether a goal is supported by a given database Start with the goal -Applicable RULES are found by matching ACTION parts with the GOAL C 1 C n GOAL Now the conditional part: C 1 C n is checked against the DB. If all are (after matching) in DB, the solution is reached. If C i is not in DB , we treat it as a SUBGOAL and repeat.
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