6. This question explores how having an explicit semantics can be used to debug programs. The file elect_bug2.ail in the AILog distribution on the book website is an axiomatization of the electrical wiring domain of Figure 5.2, but it contains a buggy clause (one that is false in the intended interpretation shown in the figure). The aim of this exercise is to use AILog to find the buggy clause, given the denotation of the symbols given in Example 5.7. To find the buggy rule, you do not even need to look at the knowledge base! (You can look at the knowledge base to find the buggy clause if you like, but that will not help you in this exercise.) All you must know is the meaning of the symbols in the program and what is true in the intended interpretation.

The query lit_l1 can be proved, but it is false in the intended interpretation. Use the how questions of AILog to find a clause whose head is false in the intended interpretation and whose body is true. This is a buggy rule.