Safe folding/unfolding with conditional narrowing -- Optimal non-deterministic functional logic computations -- A semantic basis for termination analysis of logic programs and its realization using symbolic norm constraints -- Parallelizing functional programs by generalization -- Higher-order equational unification via explicit substitutions -- Parameterised higher-order algebraic specifications -- Higher-order lazy narrowing calculus: A computation model for a higher-order functional logic language -- On composable properties of term rewriting systems -- Needed reductions with context-sensitive rewriting -- Conditional term graph rewriting -- Lazy narrowing with parametric order sorted types -- Termination of algebraic type systems: The syntactic approach -- Proof net semantics of proof search computation -- Explicit substitutions for the ??-calculus -- A left-linear variant of ?? -- Perpetuality and uniform normalization -- Model generation with existentially quantified variables and constraints -- Optimal left-to-right pattern-matching automata.

This book constitutes the refereed proceedings of the 6th International Conference on Algebraic and Logic Programming, ALP '97 and the 3rd International Workshop on Higher-Order Algebra, Logic and Term Rewriting, HOA '97, held jointly in Southampton, UK, in September 1997. The 18 revised full papers presented in the book were selected from 31 submissions. The volume is divided in sections on functional and logic programming, higher-order methods, term rewriting, types, lambda-calculus, and theorem proving methods.