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Reports Year : 1998

Rigid Reachability


We show that rigid reachability, the non-symmetric form of rigid E-unification, is undecidable already in the case of a single constraint. From this we infer the undecidability of a new rather restricted kind of second-order unification. We also show that certain decidable subclasses of the problem which are PTIME-complete in the equational case become EXPTIME-complete when symmetry is absent. By applying automata-theoretic methods, simultaneous monadic rigid reachability with ground rules is shown to be in EXPTIME.
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Dates and versions

inria-00098741 , version 1 (26-09-2006)


  • HAL Id : inria-00098741 , version 1


Harald Ganzinger, Florent Jacquemard, Margus Veanes. Rigid Reachability. [Intern report] 98-R-388 || ganzinger98a, 1998, 24 p. ⟨inria-00098741⟩
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