On measuring nondeterminism in regular languages
Information and Computation
On the relation between ambiguity and nondeterminism in finite automata
Information and Computation
Measures of nondeterminism for pushdown automata
Journal of Computer and System Sciences
Pushdown automata with bounded nondeterminism and bounded ambiguity
Theoretical Computer Science - Special issue: Latin American theoretical informatics
The Degrees of Nondeterminism in Pushdown Automata
FCT '87 Proceedings of the International Conference on Fundamentals of Computation Theory
Computations with a restricted number of nondeterministic steps (Extended Abstract)
STOC '77 Proceedings of the ninth annual ACM symposium on Theory of computing
Context-dependent nondeterminism for pushdown automata
Theoretical Computer Science
Regulated nondeterminism in pushdown automata
Theoretical Computer Science
Two-dimensional hierarchies of proper languages of lexicalized FRR-automata
Information and Computation
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
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The amount of nondeterminism that a pushdown automaton requires to recognize an input string can be measured by the minimum number of guesses that it must make to accept the string, where guesses are measured in bits of information. When this quantity is unbounded, the rate at which it grows as the length of the string increases serves as a measure of the pushdown automaton's ''rate of consumption'' of nondeterminism. We show that this measure is similar to other complexity measures in that it gives rise to an infinite hierarchy of complexity classes of context-free languages differing in the amount of the resource (in this case, nondeterminism) that they require. In addition, we show that there are context-free languages that can only be recognized by a pushdown automaton whose nondeterminism grows linearly, resolving an open problem in the literature. In particular, the set of palindromes is such a language.