Left-to-right tree pattern matching

Abstract

We propose a new technique to construct left-to-right matching automata for trees. Our method is based on the novel concept of prefix unifcation which is used to compute a certain closure of the pattern set. From the closure a kind of deterministic matching automaton can be derived immediately. We also point out how to perform the construction incrementally which makes our approach suitable for applications in which pattern sets change dynamically, such as in the Knuth-Bendix completion algorithm. Our method, like most others, is restricted to linear patterns (the case of non-linear matching can be handled as usual by checking the consistency of variable bindings in a separate pass following the matching phase).