A Lambda Prolog Based Animation of Twelf Specifications

Specifications in the Twelf system are based on a logic programming interpretation of the Edinburgh Logical Framework or LF. We consider an approach to animating such specifications using a λProlog implementation. This approach is based on a lossy translation of the dependently typed LF expressions into the simply typed lambda calculus (STLC) terms of λProlog and a subsequent encoding of lost dependency information in predicates that are defined by suitable clauses. To use this idea in an implementation of logic programming a la Twelf, it is also necessary to translate the results found for λProlog queries back into LF expressions. We describe such an inverse translation and show that it has the necessary properties to facilitate an emulation of Twelf behavior through our translation of LF specifications into λProlog programs. A characteristic of Twelf is that it permits queries to consist of types which have unspecified parts represented by meta-variables for which values are to be found through computation. We show that this capability can be supported within our translation based approach to animating Twelf specifications.