Real-Time Strict Deterministic Languages
Michael A. Harrison, Ivan M. Havel · SIAM Journal on Computing · 1972
The family of strict deterministic languages has been studied for its theoretical properties and applications to parsing. In particular, these languages have been shown to be precisely the prefix-free deterministic languages. Deterministic pushdown automata are called (quasi-)real time if they have no (only a bounded number of consecutive) null moves. It is shown that for strict deterministic languages, the quasi-real-time and real-time constraints are equivalent (except for $\{ \Lambda \} $). A grammatical characterization of these languages is also given. For quasi-real-time strict deterministic languages, an easy and elegant decision method is given for testing regularity. For all known methods of accepting deterministic languages, it is shown that the families of real-time languages are a proper subset of the full families. A relation is established among these sets, the simple deterministic languages, and some hierarchies.