Results 1  10
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15
Decidability of Code Properties
 Proc. 4th International Conference Developments in Language Theory, (G. Rozenberg, W. Thomas, Eds.) World Scientific
"... We explore the borderline between decidability and undecidability of the following question: "Let C be a class of codes. Given a machine M of type X, is it decidable whether the language L(M) lies in C or not?" for codes in general, !codes, codes of finite and bounded deciphering delay, prefix, ..."
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We explore the borderline between decidability and undecidability of the following question: "Let C be a class of codes. Given a machine M of type X, is it decidable whether the language L(M) lies in C or not?" for codes in general, !codes, codes of finite and bounded deciphering delay, prefix, suffix and bi(pre)fix codes, and for finite automata equipped with different versions of pushdown stores and counters.
Inside Vaucanson
 In Proceedings of Implementation and Application of Automata, 10th International Conference (CIAA), Sophia Antipolis
, 2005
"... Abstract. This paper presents some features of the Vaucanson platform. We describe some original algorithms on weighted automata and transducers (computation of the quotient, conversion of a regular expression into a weighted automaton, and composition). We explain how complex declarations due to th ..."
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Cited by 2 (1 self)
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Abstract. This paper presents some features of the Vaucanson platform. We describe some original algorithms on weighted automata and transducers (computation of the quotient, conversion of a regular expression into a weighted automaton, and composition). We explain how complex declarations due to the generic programming are masked from the user and finally we present a proposal for an XML format that allows implicit descriptions for simple types of automata. 1
Shrinking Language Models by Robust Approximation
 in Proc. IEEE Int'l. Conf. on Acoustics, Speech, and Signal Processing '98
, 1998
"... We study the problem of reducing the size of a language model while preserving recognition performance (accuracy and speed). A successful approach has been to represent language models by weighted finitestate automata (WFAs). Analogues of classical automata determinization and minimization algorith ..."
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We study the problem of reducing the size of a language model while preserving recognition performance (accuracy and speed). A successful approach has been to represent language models by weighted finitestate automata (WFAs). Analogues of classical automata determinization and minimization algorithms then provide a general method to produce smaller but equivalent WFAs. We extend this approach by introducing the notion of approximate determinization. We provide an algorithm that, when applied to language models for the North American Business task, achieves 2535% size reduction compared to previous techniques, with negligible effects on recognition time and accuracy. 1. INTRODUCTION An important goal of language model engineering is to produce small language models that guarantee fast and accurate automatic speech recognition (ASR). In practice we see tradeoffs: e.g., in size vs. accuracy and in accuracy vs. speed. There has been recent progress, however, on automatic methods for r...
Foliations for solving equations in groups: free, virtually free, and hyperbolic groups.
, 901
"... We give an algorithm for solving equations and inequations with rational constraints in virtually free groups. Our algorithm is based on Rips classification of measured band complexes. Using canonical representatives, we deduce an algorithm for solving equations and inequations in hyperbolic groups ..."
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We give an algorithm for solving equations and inequations with rational constraints in virtually free groups. Our algorithm is based on Rips classification of measured band complexes. Using canonical representatives, we deduce an algorithm for solving equations and inequations in hyperbolic groups (maybe with torsion). Additionnally, we can deal with quasiisometrically embeddable rational constraints. 1
FlipPushdown Automata: k + 1 Pushdown Reversals are Better than k
, 2002
"... Flippushdown automata are pushdown automata with the additional power to ip or reverse its pushdown, and were recently introduced by Sarkar. We solve most of Sarkar's open problems. In particular, we show that k+1 pushdown reversals are better than k for both deterministic and nondeterministic i ..."
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Cited by 2 (1 self)
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Flippushdown automata are pushdown automata with the additional power to ip or reverse its pushdown, and were recently introduced by Sarkar. We solve most of Sarkar's open problems. In particular, we show that k+1 pushdown reversals are better than k for both deterministic and nondeterministic ippushdown automata, i.e., there are languages which can be recognized by a deterministic ippushdown automaton with k + 1 pushdown reversals but which cannot be recognized by a kippushdown (deterministic or nondeterministic). Furthermore, we investigate closure and nonclosure properties as well as computational complexity problems such as xed and general membership.
Remarks on propagating partitionlimited ET0L systems
"... Abstract: In this paper, we sharpen the results of Gartner on the universality of partitionlimited ET0L systems by showing that such deterministic systems characterize the recursively enumerable sets, and, furthermore, the propagating deterministic partitionlimited ET0L systems characterize the pr ..."
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Abstract: In this paper, we sharpen the results of Gartner on the universality of partitionlimited ET0L systems by showing that such deterministic systems characterize the recursively enumerable sets, and, furthermore, the propagating deterministic partitionlimited ET0L systems characterize the programmed languages with appearance checking disallowing erasing productions. The main results of this paper have been announced in [10].
Closure Properties of Ordered Languages
 EATCS Bulletin
, 1996
"... . In this note, we solve questions regarding closure properties of ordered languages. Especially, ordered languages form a full abstract family of recursive languages which is neither intersection nor complementationclosed. 1 Introduction and Definitions Ordered languages (or equivalently, forbid ..."
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. In this note, we solve questions regarding closure properties of ordered languages. Especially, ordered languages form a full abstract family of recursive languages which is neither intersection nor complementationclosed. 1 Introduction and Definitions Ordered languages (or equivalently, forbidden random context languages) were introduced by Fris in 1968 [4]. Therefore, they belong to the classic topics of formal language theory. Surprisingly, several points on closure properties of the corresponding language families were marked as open in the monograph [3]. Most of these questions are solved in this note. We presuppose some knowledge of formal language theory on side of the reader. Especially, the Chomsky hierarchy L(CF) ( L(CS) ( L(REC) ( L(RE) should be known. An ordered grammar is a quintuple G = (VN ; V T ; P; S; OE), where VN , V T , P , and S 2 VN are the nonterminal alphabet, terminal alphabet, set of contextfree productions, and axiom, respectively. OE is a partial ord...
Parallel Communicating Grammar Systems with Terminal Transmission
, 2000
"... We introduce a new variant of PC grammar systems, called PC grammar systems with terminal transmission, PCGSTT for short. We show that rightlinear centralized PCGSTT have nice formal language theoretic properties: they are closed under gsm mappings (in particular, under intersection with regular se ..."
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We introduce a new variant of PC grammar systems, called PC grammar systems with terminal transmission, PCGSTT for short. We show that rightlinear centralized PCGSTT have nice formal language theoretic properties: they are closed under gsm mappings (in particular, under intersection with regular sets and under and homomorphisms) and union; a slight variant is, in addition, closed under concatenation and star; their power lies between that of nparallel grammars introduced by Wood and that of matrix languages of index n, and their relation to equal matrix grammars of degree n is discussed. We show that membership for these language classes is complete for NL. In a second part of the paper, we discuss questions concerning grammatical inference of these systems. More precisely, we show that PCGSTT whose component grammars are terminal distinguishable rightlinear, a notion introduced by Radhakrishnan and Nagaraja in [29, 30], are identi able in the limit if certain data comm...
Extensional Uniformity for Boolean Circuits ∗
, 805
"... Abstract Imposing an extensional uniformity condition on a nonuniform circuit complexity class C means simply intersecting C with a uniform class L. By contrast, the usual intensional uniformity conditions require that a resourcebounded machine be able to exhibit the circuits in the circuit family ..."
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Abstract Imposing an extensional uniformity condition on a nonuniform circuit complexity class C means simply intersecting C with a uniform class L. By contrast, the usual intensional uniformity conditions require that a resourcebounded machine be able to exhibit the circuits in the circuit family defining C. We say that (C, L) has the Uniformity Duality Property if the extensionally uniform class C ∩L can be captured intensionally by means of adding socalled Lnumerical predicates to the firstorder descriptive complexity apparatus describing the connection language of the circuit family defining C. This paper exhibits positive instances and negative instances of the Uniformity Duality Property.
Efficient Learning of Some Linear Simple Matrix Languages
, 2000
"... We show that socalled deterministic even linear simple matrix grammars can be inferred in polynomial time using the querybased learnerteacher model MAT proposed by Angluin for learning deterministic regular languages in [4]. In this way, we extend the class of efficiently learnable languages beyo ..."
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We show that socalled deterministic even linear simple matrix grammars can be inferred in polynomial time using the querybased learnerteacher model MAT proposed by Angluin for learning deterministic regular languages in [4]. In this way, we extend the class of efficiently learnable languages beyond both the even linear languages and the even equal matrix languages proposed in [41, 48, 52, 53, 54, 57, 56].