A pumping lemma for deterministic context-free languages
Information Processing Letters
On measuring nondeterminism in regular languages
Information and Computation
A New Approach to Formal Language Theory by Kolmogorov Complexity (Preliminary Version)
ICALP '89 Proceedings of the 16th International Colloquium on Automata, Languages and Programming
Computations with a restricted number of nondeterministic steps (Extended Abstract)
STOC '77 Proceedings of the ninth annual ACM symposium on Theory of computing
On interacting automata with limited nondeterminism
Fundamenta Informaticae - Special issue on cellular automata
Refining nondeterminism below linear time
Journal of Automata, Languages and Combinatorics - Third international workshop on descriptional complexity of automata, grammars and related structures
Space- and time-bounded nondeterminism for cellular automata
Fundamenta Informaticae - Special issue on cellular automata
Measuring nondeterminism in pushdown automata
Journal of Computer and System Sciences
Context-dependent nondeterminism for pushdown automata
Theoretical Computer Science
Regulated nondeterminism in pushdown automata
Theoretical Computer Science
Regulated nondeterminism in pushdown automata
CIAA'07 Proceedings of the 12th international conference on Implementation and application of automata
Descriptional complexity of (un)ambiguous finite state machines and pushdown automata
RP'10 Proceedings of the 4th international conference on Reachability problems
Context-Dependent nondeterminism for pushdown automata
DLT'06 Proceedings of the 10th international conference on Developments in Language Theory
Space- and Time-Bounded Nondeterminism for Cellular Automata
Fundamenta Informaticae - Cellular Automata
On Interacting Automata with Limited Nondeterminism
Fundamenta Informaticae - Cellular Automata
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D. Vermeir and W. Savitch (Fund. Inform.4 (1981), 401-418) introduced two measures of nondeterminism for pushdown automata and showed interestingly that the second measure, which we refer to as the depth measure, yields an infinite hierarchy of language families between the deterministic context-free and general context-free languages. However, the proof given in op. cit. for this hierarchy theorem was incorrect. In this paper, using a pumping result for deterministic context-free languages we give a new proof for the strictness of the depth hierarchy. We introduce the monadic depth measure which is also shown to give rise to an infinite hierarchy of language families. Furthermore, we show that the monadic hierarchy is shifted by at most one level from the unrestricted depth hierarchy.