Using Automata to obtain Regular Expressions for Induced Actions

Abstract

Presentations of Kan extensions of category actions provide a natural framework for expressing induced actions, and therefore a range of different combinatorial problems. Rewrite systems for Kan extensions have been defined and a variation on the Knuth-Bendix completion procedure can be used to complete them -- when possible. Regular languages and automata are a useful way of expressing sets and actions, and in this paper we explain how to use rewrite systems for Kan extensions to construct automata expressing the induced action and how sets of normal forms can be calculated by obtaining language equations from the automata.