We introduce two models of parallel two-dimensional Turing machine with different possibilities of communication among control units and we compare them.
Motivated by natural language analysis we introduce restarting automata with rewriting. They are acceptors on the one hand, and (special) regulated rewriting systems on the other hand. The computation of a restarting automaton proceeds in cycles: in each cycle, a bounded substring of the input word is rewritten by a shorter string, and the computation… (More)
We provide a formal model of a stratificational dependency approach to natural language description. This formal model is motivated by an elementary method of analysis by reduction, which serves for describing correct sentence analysis. The model is based on enhanced restarting automata that assign a set of parallel dependency structures to every reduction… (More)
The restarting automaton is a special kind of the linear bounded automaton with a read/write window of fixed length. It works in cycles, reducing the length of the actual word in each cycle. We study several versions of restarting automata and we show several hierarchies of language classes recognized by them with respect to the size of the… (More)