Uncertainty-valued horn clauses

Abstract

There are many forms of uncertainty, each usually again having more than one theoretical model. Therefore, a very flexible kind of uncertainty-valued Horn clauses is introduced in RELFUN in section 1. They have a head, several premises and an uncertainty factor, which represents the uncertainty of the clause. The premises are all "functional" in the sense that their returned value is again an uncertainty value. These premises and the uncertainty factor of an uncertainty rule become embedded into the arguments of a combination function when translating uncertainty clauses into footed clauses (non-ground, non-deterministic functions in RELFUN, which can then be compiled as usual). The combination function can be modified by the user. It may be a built-in or a user-defined function, either of which may be computed as the value of a higher-order function. In section 2, an application of uncertainty clauses to the uncertain concept of a "pet holder", according to German law, is described. This and another example are then fully demonstrated in appendix A. Finally, appendix B gives a listing of the complete uncertainty translator in LISP.