A pragmatic reconstruction of λProlog

AbstractλProlog is a logic programming language in which hereditary Harrop formulas generalize Horn formulas, and simply typed λ-terms generalize Prolog terms. One may wonder if these extensions are simultaneously required, and if useful subsets of λPrologcan be defined, at least for pedagogical purposes. We answer this question by exhibiting a network of necessity links between the new features of λProlog. The starting point of the network is the demand for programming by structural induction on λ-terms, and the necessity links give a rationale for such a programming style