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RULE 1:
If the result of switching on the headlights is nothing happens or the result of trying the starter is nothing happens Then the recommended action is recharge or replace the battery |
RULE 2:
If the result of trying the starter is the car cranks normally and a gas smell is not present when trying the starter Then the gas tank is empty with 90% confidence |
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RULE 3:
If the gas tank is empty Then the recommended action is refuel the car |
RULE 4:
If the result of trying the starter is the car cranks normally and a gas smell is present when trying the starter Then the recommended action is wait 10 minutes, then restart flooded car |
Each rule consists of an if part called the premise or antecedent (shown in blue) and a then part called the consequent or conclusion (shown in green). When the if part is true, the rule is said to fire and the then part is asserted -- it is considered to be a fact.
Rule results are often combined to reach a conclusion. The goal of the auto diagnosis is to find a recommended action: what to do to get the car started. Rule 3 tells what to do if the gas tank is empty and rule 2 could prove that the gas tank is empty. If rule 2 fires, rule 3 will also fire and provide a recommended course of action.
The consequent in rule 2 is asserted with 90% confidence. This means that if the rule's premise is true, we are only 90% certain that the car is out of gas. Our computer-based expert might be willing to accept this level of confidence to fire rule 3 and recommend an action.