Handling Left-Quadratic Rules When Completing Tree Automata
Abstract
This paper addresses the following general problem of tree regular model-checking: decide whether the intersection of R*(L) and Lp is empty, where R* is the reflexive and transitive closure of a successor relation induced by a term rewriting system R, and L and Lp are both regular tree languages. We develop an automatic approximation-based technique to handle this -- undecidable in general -- problem in the case when term rewriting system rules are left-quadratic. The most common practical case is handled this way.
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