On Unambiguous Regular Tree Languages of Index (0, 2)
Details
Serval ID
serval:BIB_5DC9CA1E3285
Type
Inproceedings: an article in a conference proceedings.
Collection
Publications
Institution
Title
On Unambiguous Regular Tree Languages of Index (0, 2)
Title of the conference
24th EACSL Annual Conference on Computer Science Logic, CSL 2015, September 7-10, 2015, Berlin, Germany
Publication state
Published
Issued date
2015
Peer-reviewed
Oui
Volume
41
Series
Leibniz International Proceedings in Informatics
Pages
534-548
Language
english
Notes
DBLP:conf/csl/DuparcFH15
Abstract
Unambiguous automata are usually seen as a natural class of automata in-between deterministic and nondeterministic ones. We show that in case of infinite tree languages, the unambiguous ones are topologically far more complicated than the deterministic ones. We do so by providing operations that generate a family (A_{alpha})_{alpha < phi_2(0)} of unambiguous automata such that: 1. It respects the strict Wadge ordering: alpha < beta if and only if A_{alpha} <_W A_{beta}. This can be established without the help of any determinacy principle, simply by providing effective winning strategies in the underlying games. 2. Its length (phi_2(0)) is the first fixpoint of the ordinal function that itself enumerates all fixpoints of the ordinal exponentiation x |-> omega^x: an ordinal tremendously larger than (omega^(omega))^3 +3 which is the height of the Wadge hierarchy of deterministic tree languages as uncovered by Filip Murlak. 3. The priorities of all these parity automata only range from 0 to 2.
Keywords
s Tree Automata, Unambiguity, Wadge Hierarchy
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Create date
06/04/2016 17:18
Last modification date
07/07/2021 12:13