Previous Year Exam Questions Topic: Expert Systems and Rule-based Reasoning

Given a rule-based Expert System with 9 rules whose purpose is to advise you on how your health is influenced by certain foods and other factors. The rules are: R1: IF you eat beef or eggs THEN high cholesterol R2: IF you eat fish or poultry and no beef THEN low cholesterol R3: IF you eat no beef and no fish and no poultry THEN low cholesterol R4: IF you are Catholic and today is Friday THEN you eat no fish and no beef R5: IF you are a vegetarian THEN you eat no fish, no beef and no poultry R6: IF low cholesterol THEN healthy R7: IF high cholesterol THEN unhealthy R8: IF you eat veal THEN you eat beef R9: If you work 6 hours or less today THEN it is Friday

1.Run a forward chaining system to determine the health state of a person who eats veal. Final goal: the person is Unhealthy. Rules that fired are: R8, R1, R7 & Stopped. Note: Conditions of other rules are not satisfied thus they are not executed in the forward chaining system to conclude the “unhealthy” decision.

2. What if you are catholic, eat poultry and work 4 hours today? Advise the person on his health situation. Justify your answer. Final Recommendation: The person is Healthy. Rules that fired are: R9, R4, R2, R6 & Stopped. Students are required to give reason for why R9 is first fired? Why was it chained to R4, etc. Also, students need to mention why other rules are not used. An example is given below: – R1 is not used because no clue on ‘egg’. – R3 is not fired because the person eats poultry. So the condition is false. – R5 is not used since not told that he is a vegetarian. – R8 is not fired since ‘”eat veal” is unknown.

Suppose you have the following rules in your Knowledge base: Rule 1: IF X is true AND B is true AND E is true THEN Y is true Rule 2: IF Y is true AND D is true THEN Z is true Rule 3: IF A is true THEN X is true Rule 4: IF Y is true AND C is true THEN W is true Suppose a forward chaining (data-driven) system is used. What “goal” would the system return if A, B, C, E are true? Explain how the result is obtained (e.g. show the reasoning path). Answer: The system will return “W” as the goal. How? By firing R3, R1, and R4. Other rules all failed. Answer: The system will return “W” as the goal. How? By firing R3, R1, and R4. Other rules all failed.