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.