Logical control of an elevator with defeasible logic

The elevator control program of Dyck and Caines (1995) can be implemented more concisely in d-Prolog, a defeasible logic programming system developed by Nute (1992, 1996, 1997). To demonstrate this, the program is recast, first into ordinary Prolog and then into d-Prolog. In defeasible logic, more specific rules take precedence over more general ones. Thus, the d-Prolog programmer can state general rules and then give explicit exceptions, just as humans do when explaining complex regularities to each other.