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RESEARCH PRODUCT

Varieties and Covarieties of Languages (Extended Abstract)

Enric Cosme LlópezAdolfo Ballester-bolinchesJan Rutten

subject

Discrete mathematicsGeneral Computer ScienceCoalgebraData ScienceStructure (category theory)Duality (optimization)equationalgebraAutomataTheoretical Computer ScienceAlgebravarietyReachabilityDeterministic automatonComputingMethodologies_DOCUMENTANDTEXTPROCESSINGcoequationObservabilityIsomorphismcovarietyVariety (universal algebra)coalgebraComputer Science::Formal Languages and Automata TheoryComputer Science(all)Mathematics

description

AbstractBecause of the isomorphism (X×A)→X≅X→(A→X), the transition structure of a deterministic automaton with state set X and with inputs from an alphabet A can be viewed both as an algebra and as a coalgebra. This algebra-coalgebra duality goes back to Arbib and Manes, who formulated it as a duality between reachability and observability, and is ultimately based on Kalmanʼs duality in systems theory between controllability and observability. Recently, it was used to give a new proof of Brzozowskiʼs minimization algorithm for deterministic automata. Here we will use the algebra-coalgebra duality of automata as a common perspective for the study of both varieties and covarieties, which are classes of automata and languages defined by equations and coequations, respectively. We make a first connection with Eilenbergʼs definition of varieties of languages, which is based on the classical, algebraic notion of varieties of (transition) monoids.

10.1016/j.entcs.2013.09.005http://dx.doi.org/10.1016/j.entcs.2013.09.005