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Erschienen in:
2005 | OriginalPaper | Buchkapitel
Congruences for Visibly Pushdown Languages
verfasst von : Rajeev Alur, Viraj Kumar, P. Madhusudan, Mahesh Viswanathan
Erschienen in: Automata, Languages and Programming
Verlag: Springer Berlin Heidelberg
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We study congruences on words in order to characterize the class of visibly pushdown languages (
Vpl
), a subclass of context-free languages. For any language
L
, we define a natural congruence on words that resembles the syntactic congruence for regular languages, such that this congruence is of finite index if, and only if,
L
is a
Vpl
. We then study the problem of finding canonical minimal deterministic automata for
Vpl
s. Though
Vpl
s in general do not have unique minimal automata, we consider a subclass of VPAs called
k
-module single-entry VPAs that correspond to programs with recursive procedures without input parameters, and show that the class of well-matched
Vpl
s do indeed have unique minimal
k
-module single-entry automata. We also give a polynomial time algorithm that minimizes such
k
-module single-entry VPAs.