Skeletons and Predicate Specifications

Skeletal information refers to the name and arity of the primary functor of a term. A skeleton for a functor f/n is any structure of the form f(Arg₁,...,Arg_n) where Arg_i can be any term. Thus the skeletal information derived from the skeletons f(1,2) and f(A,B) would be the same. A return skeleton is a specific application of this notion to answer returns. From it, one may discern the size of the template for a given subgoal. Finally, we assume that a predicate specification for a predicate p and arity n, represented as PredSpec below, can be given either using the notation p/n or as a skeleton, p(t₁,...,t_n) for any term t_i.