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Folk theorems on the determinization and minimization of timed automata. (English) Zbl 1185.68401
Summary: Timed automata are known not to be complementable or determinizable. Natural questions are, then, could we check whether a given TA enjoys these properties? These problems are not algorithmically solvable. Minimizing the “resources” of a TA (number of clocks or size of constants) are also unsolvable problems. In this paper we provide simple undecidability proofs using a “constructive” version of the problems where we require not just a yes/no answer, but also a “witness”. Proofs are then simple reductions from the universality problem. Recent work of Finkel shows that the corresponding decision problems are also undecidable [O. Finkel, Bull. Eur. Assoc. Theor. Comput. Sci. EATCS 87, 185–190 (2005; Zbl 1169.68467)].

##### MSC:
 68Q45 Formal languages and automata
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##### References:
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