A descriptive Mode Inference for Logic

In general, an n-ary predicate (relation) describes the relationship among its arguments, and such that no argument has to be of a special mode. The uniication and the resolution (SLDNF-resolution) do capture this state of aaair. Hence, the aim of logic programming is in some point approximatively achieved if the system is able to automatically determine the descriptive mode of an n-ary predicate symbol with respect to a logic program. The descriptive mode of an n-ary predicate symbol with respect to a logic program indicates the instantiation of the arguments of that n-ary predicate symbol when it occurs in a goal. To get a sound descriptive mode for an n-ary predicate symbol we consider the abstraction of terms and hence of a set of clauses, the uniication of abstract terms and deene an NJSLDT-derivation. The descriptive mode inference determines which arguments of an n-ary predicate symbol in a goal become closed or partially instantiated or remain variable. Since the mode of an n-ary predicate symbol does innuence the operational semantics of that predicate, this information may be used by a compiler for the purpose of eeciency. The mode inference will also help automatically determine the literal to be selected when constructing an SLDNF-derivation, weaken the condition of allowedness, automatically prove the termination of logic programs for a large class of programs, and detect some errors at compile time.