Transfinite reductions in orthogonal term rewriting systems -- Redex capturing in term graph rewriting (concise version) -- Rewriting, and equational unification: the higher-order cases -- Adding algebraic rewriting to the untyped lambda calculus (extended abstract) -- Incremental termination proofs and the length of derivations -- Time bounded rewrite systems and termination proofs by generalized embedding -- Detecting redundant narrowing derivations by the LSE-SL reducibility test -- Unification, weak unification, upper bound, lower bound, and generalization problems -- AC unification through order-sorted AC1 unification -- Narrowing directed by a graph of terms -- Adding homomorphisms to commutative/monoidal theories or how algebra can help in equational unification -- Undecidable properties of syntactic theories -- Goal directed strategies for paramodulation -- Minimal solutions of linear diophantine systems : bounds and algorithms -- Proofs in parameterized specifications -- Completeness of combinations of constructor systems -- Modular higher-order E-unification -- On confluence for weakly normalizing systems -- Program transformation and rewriting -- An efficient representation of arithmetic for term rewriting -- Query optimization using rewrite rules -- Boolean algebra admits no convergent term rewriting system -- Decidability of confluence and termination of monadic term rewriting systems -- Bottom-up tree pushdown automata and rewrite systems -- On relationship between term rewriting systems and regular tree languages -- The equivalence of boundary and confluent graph grammars on graph languages of bounded degree -- Left-to-right tree pattern matching -- Incremental techniques for efficient normalization of nonlinear rewrite systems -- On fairness of completion-based theorem proving strategies -- Proving equational and inductive theorems by completion and embedding techniques -- Divergence phenomena during completion -- Simulating Buchberger's algorithm by Knuth-Bendix completion -- On proving properties of completion strategies -- On ground AC-completion -- Any ground associative-commutative theory has a finite canonical system -- A narrowing-based theorem prover -- ANIGRAF: An interactive system for the animation of graph rewriting systems with priorities -- Emmy: A refutational theorem prover for first-order logic with equations -- The tecton proof system -- Open problems in rewriting.

This volume contains the proceedings of the Fourth International Conference on Rewriting Techniques and Applications (RTA-91), held in Como, Italy, April 10-12, 1991. The volume includes 40 papers on a wide variety of topics including: term rewriting systems, equational unification, algebraic rewriting, termination proofs, generalization problems, undecidable properties, parametrized specifications, normalizing systems, program transformation, query optimization, tree languages, graph languages, theorem proving systems, completion, graph rewriting systems, and open problems.