Alternation of Restarting Automata

Restarting automata have been introduced as a formal tool to model the analysis by reduction, which is a linguistic technique to analyze sentences of natural languages. In earlier works, we have only studied the nondeterministic version of restarting automata. In order to obtain a model of parallel computations, here we propose the notion of alternating restarting automata that have the power of universal choice in addition to existential choice. In this paper, we study the expressive power of alternating restarting automata, and investigate the inclusion relations between the classes of languages accepted by various types of alternating restarting automata. Finally, we summarize these inclusion results by a hierarchy in a diagram.