A Decidable Extension of Data Automata

Data automata on data words is a decidable model proposed by Bojańczyk et al. in 2006. Class automata, introduced recently by Bojańczyk and Lasota, is an extension of data automata which unifies different automata models on data words. The nonemptiness of class automata is undecidable, since class automata can simulate two-counter machines. In this paper, a decidable model called class automata with priority class condition, which restricts class automata but strictly extends data automata, is proposed. The decidability of this model is obtained by establishing a correspondence with priority multicounter automata. This correspondence also completes the picture of the links between various class conditions of class automata and various models of counter machines. Moreover, this model is applied to extend a decidability result of Alur, Černý and Weinstein on the algorithmic analysis of array-accessing programs.