Factorizations of Regular Hedge Languages

Abstract

Regular hedge languages are an extension of regular tree languages that received renewed attention since their recognition as a formal model of XML schemata. They share several properties with regular languages, but their study is more involved because we need to analyze regularities of sequences of trees instead of words. We show that one shared property is the existence of only finitely many language factors and the possibility to compute and arrange them in a factor matrix with some remarkable properties. We outline an algorithm for the computation of the factor matrix and indicate an application of the factor matrix of an RHL to the solution of a concrete language reconstruction problem.