1. Rule-based Systems Given facts: A, B Conflict resolution: FCFS R1: IF A and D

Question

1. Rule-based Systems Given facts: A, B Conflict resolution: FCFS R1: IF A and D R2: IF C and D R3: IF B and E R4: IF B R5: IF F THEN E THEN F THEN F THEN D THEN G 1) What can be concluded by Forward Chaining? Show the sequence of rules fired and the facts added to the working memory in each sequence 2) Can a goal G be achieved by Backward Chaining? Show the sequence of rules checked, i.e, how the search for rules proceeds in a depth-first manner. Apply FCFS when branching (Gie, try the branch with the first rule first).

Explanation / Answer

1) By forward chaining conclusion is D

As in forward chaining we begin with the available data and uses their inference rules to extract more data

Execution will be like below:

Step 1: IF A and D => False (as we know only A is true as fact)

Step 2: IF C and D => false (as we know only A and B is true as fact)

Step 3: IF B and E => false (as we know only B is true as fact)

Step 4: If B => True Hence output comes as D (Now D is also true)

Step 5: IF F => False (as we know only A, B and D is true as fact)

2) Yes, because, now the steps will be as below

By Backward chaining rule #5 says G is true if F is true

Goal is to prove F as true

rule #3 states F is true if B and E is true

similarly rule#1 will become

E is true If A and D are true

Goal is to get D

rule #4 gives D is true if B is true, which is a fact hence we get D as true

=> rule #1 is true and we get E

=> rule #3 is true and then we get F

=> rule #5 is true and we get G

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