#@artificial intelligence, programming, language@# A The programmer writes a "database" of " facts", e.g. wet(water). ("water is wet") and " rules", e.g. mortal(X) :- human(X). ("X is mortal is implied by X is human"). Facts and rules are The user supplies a " goal" which the system attempts to involves matching the current goal against each fact or the left hand side of each rule using " unification". If the goal matches a fact, the goal succeeds; if it matches a rule then the process recurses, taking each sub-goal on the right hand side of the rule as the current goal. If all sub-goals succeed then the rule succeeds. control eventually returns to the choice point and subsequent necessary to make the fact or the left hand side of the rule match a goal. Unification binds these variables to the corresponding subterms of the goal. Such bindings are chosen and are undone when backtracking reaches that choice point. The user is informed of the success or failure of his first goal and if it succeeds and contains variables he is told what values of those variables caused it to succeed. He can then ask for alternative solutions. (1997-07-14)
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