Bottom-up rewriting for words and terms
Résumé
For the whole class of linear term rewriting systems, we define bottom-up rewriting which is a restriction of the usual notion of rewriting. We show that bottom-up rewriting effectively inverse-preserves recognizability. The Bottom-Up class (BU) is, by definition, the set of linear systems for which every derivation can be replaced by a bottom-up derivation. Since membership to BU turns out to be undecidable, we are led to define more restricted classes: the classes SBU(k), for k in N of Strongly Bottom-Up(k) systems for which we show that membership is decidable. We define the class SBU of Strongly Bottom-Up systems which is the union for all integers k of SBU(k). We give a polynomial-time sufficient condition for a system to be in SBU. The class SBU contains (strictly) several classes of systems which were already known to inverse preserve recognizability: the inverse left-basic semi-Thue systems (viewed as unary term rewriting systems), the linear growing term rewriting systems, the inverse Linear-Finite-Path-Ordering systems.