Extensions of Logic Programming

Volume 798 of the series Lecture Notes in Computer Science pp 206-221


A proposal for modules in λProlog

  • Dale MillerAffiliated withComputer Science Department, University of Pennsylvania


Higher-order hereditary Harrop formulas, the underlying logical foundation of λProlog [NM88], are more expressive than first-order Horn clauses, the logical foundation of Prolog. In particular, various forms of scoping and abstraction are supported by the logic of higherorder hereditary Harrop formulas while they are not supported by firstorder Horn clauses. Various papers have argued that the scoping and abstraction available in this richer logic can be used to provide for modular programming [Mil89b], abstract data types [Mil89a], and state encapsulation [HM90]. None of these papers, however, have dealt with the problems of programming-in-the-large, that is, the essentially linguistic problems of putting together various different textual sources of code found, say, in different files on a persistent store into one logic program. In this paper, I propose a module system for λProlog and shall focus mostly on its static semantics.