This volume contains the papers which have been accepted forpresentation atthe Third International Symposium onProgramming Language Implementation andLogic Programming(PLILP '91) held in Passau, Germany, August 26-28, 1991.

Standard ML of New Jersey.- Adding equations to NU-Prolog.- Extraction of functional from logic program.- The MAS specification component.- Domesticating imperative constructs so that they can live in a functional world.- Logic-based specification of visibility rules.- Optimal instruction scheduling using constraint logic programming.- An architectural model for OR-parallellism on distributed memory systems.- FRATS: A parallel reduction strategy for shared memory.- Narrowing as an incremental constraint satisfaction algorithm.- The implementation of lazy narrowing.- Semantics-directed generation of a Prolog compiler.- A framework to specify database update views for Prolog.- Concepts for a modular and distributed Prolog language.- From parlog to polka in two easy steps.- Precedences in specifications and implementations of programming languages.- A randomized heuristic approach to register allocation.- Generating efficient code from data-flow programs.- On the borderline between grammars and programs.- Efficient incremental evaluation of higher order attribute grammars.- Profit: A system integrating logic programming and attribute grammars.- Towards a meaning of LIFE.- U-log, an ordered sorted logic with typed attributes.- Compilation of predicate abstractions in higher-order logic programming.- Abstract interpretation: A kind of magic.- Abstract interpretation for type checking.- A technique for recursive invariance detection and selective program specialization.- Dynamic detection of determinism in functional logic languages.- Unfolding — definition — folding, in this order, for avoiding unnecessary variables in logic programs.- Efficient integration of simplification into Prolog.- Lazy evaluation in logic.- S-SLD-resolution — An operational semantics for logicprograms with external procedures.- Operational semantics of constraint logic programming over finite domains.- Constraints for synchronizing coarse-grained sequential logic processes.- Extending execution trees for debugging and animation in logic programming.- A narrowing-based theorem prover.- The ALF system.- Experiences with gentle: Efficient compiler construction based on logic programming.- The system FLR ( Fast laboratory for recomposition ).- Multilanguage interoperability.- Short overview of the CLPS system.