Categorical Rewriting

Term Rewriting Systems (TRSs) are widely used throughout computer science as they form an abstract model of computation. However, the concrete syntactic nature of term rewriting often obscures the underlying structure and a more abstract semantics is therefore needed. Abstract Reduction Systems provide a relational semantics for TRSs, but unfortunately these relations do not posses enough structure to adequately model several key concepts. Hence the relational model is used mainly as an organisational tool with the difficult results proved directly at the syntactic level.

We believe that rewriting needs a semantics at an intermediate level of abstraction between the syntax and the relational model. Originally it was hoped that 2-categories would provide such a model but despite some one-off results, 2-categorical models of TRSs have failed to make a lasting impact. Our research focuses on applying the theory of enriched monads to term rewriting with very promising results. These monads have been used to give semantic proofs of some difficult results in modular term rewriting. We are currently using monads to tackle open problems in modular term rewriting for conditional TRSs and unions which permit limited sharing.

Journal Papers

Research Papers


Author: Neil Ghani
Email: ng13@mcs.le.ac.uk
Tel: 44 (0)116 252 3807
Last Update: June 22 2000

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