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Journal Articles International Journal of Foundations of Computer Science Year : 2000

Rigid reachability, the non-symmetric form of rigid E-unification

Abstract

We show that rigid reachability, the non-symmetric form of rigid E-unification, is already undecidable in the case of a single constraint. From this we infer the undecidability of a new and 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 PSPACE-complete. Moreover, we identify two decidable non-monadic fragments that are complete for EXPTIME.
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Dates and versions

inria-00099097 , version 1 (26-09-2006)

Identifiers

  • HAL Id : inria-00099097 , version 1

Cite

Harald Ganzinger, Florent Jacquemard, Margus Veanes. Rigid reachability, the non-symmetric form of rigid E-unification. International Journal of Foundations of Computer Science, 2000, 11 (1), pp.3-27. ⟨inria-00099097⟩
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