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Two-Way Unary Temporal Logic over Trees (0904.4119v2)
Published 27 Apr 2009 in cs.LO
Abstract: We consider a temporal logic EF+F-1 for unranked, unordered finite trees. The logic has two operators: EF\phi, which says "in some proper descendant \phi holds", and F-1\phi, which says "in some proper ancestor \phi holds". We present an algorithm for deciding if a regular language of unranked finite trees can be expressed in EF+F-1. The algorithm uses a characterization expressed in terms of forest algebras.