Title
A topological approach to transductions
Abstract
This paper is a contribution to the mathematical foundations of the theory of automata. We give a topological characterization of the transductions τ from a monoid M into a monoid N, such that if R is a recognizable subset of N, τ-1(R) is a recognizable subset of M. We impose two conditions on the monoids, which are fullfilled in all cases of practical interest: the monoids must be residually finite and, for every positive integer n, must have only finitely many congruences of index n. Our solution proceeds in two steps. First we show that such a monoid, equipped with the so-called Hall distance, is a metric space whose completion is compact. Next we prove that τ can be lifted to a map τ from M into the set of compact subsets of the completion of N. This latter set, equipped with the Hausdorff metric, is again a compact monoid. Finally, our main result states that τ-1 preserves recognizable sets if and only if τ is continuous.
Year
DOI
Venue
2005
10.1016/j.tcs.2005.03.029
Theor. Comput. Sci.
Keywords
DocType
Volume
recognizable subset,compact monoid,monoid M,monoid N,compact subsets,recognizable set,index n,latter set,metric space,positive integer n,topological approach
Journal
340
Issue
ISSN
Citations 
2
0304-3975
9
PageRank 
References 
Authors
0.74
9
2
Name
Order
Citations
PageRank
Jean-Eric Pin163267.86
Pedro V. Silva214129.42