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State complexity of basic operations on nondeterministic finite automata
 In Implementation and Application of Automata: 7th International Conference, CIAA 2002 (2003), J.M. Champarnaud and D. Maurel, Eds
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On the Determinization of Weighted Finite Automata
 SIAM J. Comput
, 1998
"... . We study determinization of weighted finitestate automata (WFAs), which has important applications in automatic speech recognition (ASR). We provide the first polynomialtime algorithm to test for the twins property, which determines if a WFA admits a deterministic equivalent. We also provide ..."
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Cited by 18 (0 self)
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. We study determinization of weighted finitestate automata (WFAs), which has important applications in automatic speech recognition (ASR). We provide the first polynomialtime algorithm to test for the twins property, which determines if a WFA admits a deterministic equivalent. We also provide a rigorous analysis of a determinization algorithm of Mohri, with tight bounds for acyclic WFAs. Given that WFAs can expand exponentially when determinized, we explore why those used in ASR tend to shrink. The folklore explanation is that ASR WFAs have an acyclic, multipartite structure. We show, however, that there exist such WFAs that always incur exponential expansion when determinized. We then introduce a class of WFAs, also with this structure, whose expansion depends on the weights: some weightings cause them to shrink, while others, including random weightings, cause them to expand exponentially. We provide experimental evidence that ASR WFAs exhibit this weight dependence. ...
The Topological Approach to the Limitedness Problem on Distance Automata
, 1998
"... this paper, we present the topological approach to the limitedness problem on distance automata. Our techniques has been improved so that the Brown's result is no longer needed. The main mathematical tools used are the local structure theory for nite semigroup [13] and some basic topological i ..."
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Cited by 8 (1 self)
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this paper, we present the topological approach to the limitedness problem on distance automata. Our techniques has been improved so that the Brown's result is no longer needed. The main mathematical tools used are the local structure theory for nite semigroup [13] and some basic topological ideas. Most of the technical results in this paper except Lemma 3.9 and Lemma 3.10 were obtained in ([14], [15]). Besides for the sake of completeness, we include all the proofs because many of them have been reworked for better presentations
Communication Complexity Method for Measuring Nondeterminism in Finite Automata
, 2000
"... While deterministic finite automata seem to be well understood, surprisingly many important problems concerning nondeterministic finite automata (nfa's) remain open. One such problem ..."
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Cited by 7 (1 self)
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While deterministic finite automata seem to be well understood, surprisingly many important problems concerning nondeterministic finite automata (nfa's) remain open. One such problem
Measures of Nondeterminism in Finite Automata
, 2000
"... While deterministic finite automata seem to be well understood, surprisingly many important problems concerning nondeterministic finite automata (nfa's) remain open. One such problem area is the study of different measures of nondeterminism in finite automata and the estimation of the sizes of ..."
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Cited by 5 (0 self)
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While deterministic finite automata seem to be well understood, surprisingly many important problems concerning nondeterministic finite automata (nfa's) remain open. One such problem area is the study of different measures of nondeterminism in finite automata and the estimation of the sizes of minimal nondeterministic finite automata. In this paper the concept of communication complexity is applied in order to achieve progress in this problem area. The main results are as follows: 1. Deterministic communication complexity provides lower bounds on the size of unambiguous nfa's. Applying this fact, the proofs of several results about nfa's with limited ambiguity can be simplified. 2. For an nfa A we consider the complexity measures advice_A(n) as the number of advice bits, ambig_A(n) as the number of accepting computations, and leaf_A(n) as the number of computations for worst case inputs of size n. These measures are correlated as follows (assuming that the nfa A is minimal): advice_A(n), ambig_A(n) lowerequal leaf_A(n) lowerequal O(advice_A(n) times ambig_A(n)). 3. leaf_A(n) is always either a constant, between linear and polynomial in n, or exponential in n. 4. There is a family of languages KON_{k^2} with an exponential size gap between nfa's with polynomial leaf number/ambiguity and nfa's with ambiguity k. This partially provides an answer to the open problem posed by Ravikumar and Ibarra [SIAM J. Comput. 18 (1989), 12631282], and Hing Leung [SIAM J. Comput. 27 (1998), 10731082]. Keywords: finite automata, nondeterminism, limited ambigiuty, descriptional complexity, communication complexity
A SURVEY OF LIMITED NONDETERMINISM
, 2003
"... Nondeterminism is typically used as an inherent part of the computational models used in computational complexity. However, much work has been done looking at nondeterminism as a separate resource added to deterministic machines. This survey examines several different approaches to limiting the amou ..."
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Nondeterminism is typically used as an inherent part of the computational models used in computational complexity. However, much work has been done looking at nondeterminism as a separate resource added to deterministic machines. This survey examines several different approaches to limiting the amount of nondeterminism, including Kintala and Fischer’s β hierarchy, and Cai and Chen’s guessandcheck model.
Refining Nondeterminism Below LinearTime
, 2001
"... Multitape Turing machines with a restricted number of nondeterministic steps are investigated. Fischer and Kintala showed an in nite nondeterministic hierarchy of properly included realtime languages between the deterministic languages and the logbounded nondeterministic languages. This result ..."
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Multitape Turing machines with a restricted number of nondeterministic steps are investigated. Fischer and Kintala showed an in nite nondeterministic hierarchy of properly included realtime languages between the deterministic languages and the logbounded nondeterministic languages. This result is extended to time complexities in the range between realtime and lineartime, and is generalized to arbitrary dimensions.
Lexicalized RRWWAutomata – A New Measure for The Degree of Nondeterminism of (ContextFree) Languages ∗
, 2007
"... Restarting automata can be seen as analytical variants of classical automata as well as of regulated rewriting systems. We study a measure for the degree of nondeterminism of (contextfree) languages in terms of deterministic restarting automata that are (strongly) lexicalized. This measure is based ..."
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Restarting automata can be seen as analytical variants of classical automata as well as of regulated rewriting systems. We study a measure for the degree of nondeterminism of (contextfree) languages in terms of deterministic restarting automata that are (strongly) lexicalized. This measure is based on the number of auxiliary symbols (categories)