Journal:Informatica
Volume 10, Issue 1 (1999): Special Issue on Programming Theory, Information System Engineering, Software Engineering, and Artificial Intelligence, pp. 27–44
Abstract
CF-expressions are defined which generalize the regular one. It is established that so called pseudo-coiterating CF-expressions characterize the regular sets. The results are used to develop some more characterizations of the regular sets: the pseudo-coiterating D-graphs and the pseudo-coiterating pushdown automata (PDAs). An algorithm is presented for deciding whether a device of three mentioned types is pseudo-coiterating or not. Apparently, the pseudo-coiterating PDAs form the most large of classes of PDAs the solvability of the question of belonging to which was proved and which are known as characterizations of the regular sets.
Journal:Informatica
Volume 8, Issue 1 (1997), pp. 43–56
Abstract
The paper present a proposed approach in the context-free language theory. The main new notion is a graph defining a pushdown automaton (PDA). Each vertex of such graph is a pair (state, stack symbol). Each edge corresponds to a “command” and is labelled by input portion being read by the command and by a “charge” describing the stack word transformation. Some paths of the graph represent PDA's computations. The finite automata are a case of the pushdown graphs. The paper contains some of the author's results based on the approach – the notion of a D-language extending the notion of Dyck's language and the theorem on a representation of a context-free language as a morphical image of the intersection of a D-language with a local set.