Classes of Tree Homomorphisms with Decidable Preservation of Regularity

Abstract : Decidability of regularity preservation by a homomorphism is a well known open problem for regular tree languages. Two interesting subclasses of this problem are considered: first, it is proved that regularity preservation is decidable in polynomial time when the domain language is constructed over a monadic signature, i.e., over a signature where all symbols have arity 0 or 1. Second, decidability is proved for the case where non-linearity of the homomorphism is restricted to the root node (or nodes of bounded depth) of any input term. The latter result is obtained by proving decidability of this problem: Given a set of terms with regular constraints on the variables, is its set of ground instances regular? This extends previous results where regular constraints where not considered.
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Conference papers
Springer. FOSSACS'08, Apr 2008, Hungary. 4962, pp.127-141, 2008, LNCS


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Contributor : Sophie Tison <>
Submitted on : Wednesday, February 6, 2008 - 5:57:39 PM
Last modification on : Tuesday, May 18, 2010 - 7:12:15 PM

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Guillem Godoy, Sebastian Maneth, Sophie Tison. Classes of Tree Homomorphisms with Decidable Preservation of Regularity. Springer. FOSSACS'08, Apr 2008, Hungary. 4962, pp.127-141, 2008, LNCS. <hal-00243123>

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