Results 1  10
of
20
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 dela ..."
Abstract

Cited by 3 (2 self)
 Add to MetaCart
(Show Context)
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.
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 ..."
Abstract

Cited by 2 (0 self)
 Add to MetaCart
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
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 ..."
Abstract

Cited by 2 (1 self)
 Add to MetaCart
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
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 nondeterminis ..."
Abstract

Cited by 2 (1 self)
 Add to MetaCart
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.
On an algebraicity theorem of Kontsevich
"... Abstract. We give in a particular case a combinatorial proof of a recent algebraicity result of Kontsevich; the proof uses generalized onesided and twosided Dyck words, or equivalently, excursions and bridges. We indicate a noncommutative version of these notions, which could lead to a full proof. ..."
Abstract

Cited by 1 (0 self)
 Add to MetaCart
(Show Context)
Abstract. We give in a particular case a combinatorial proof of a recent algebraicity result of Kontsevich; the proof uses generalized onesided and twosided Dyck words, or equivalently, excursions and bridges. We indicate a noncommutative version of these notions, which could lead to a full proof. We show also a relation with pointed planar maps. Résumé. Nous donnons, dans un cas particulier, une preuve combinatoire d’un résultat récent d’algébricité de Kontsevich; la preuve utilise des mots de Dyck généralisés d’un coté et deux cotés ou de façon équivalente, excursions et ponts. Nous indiquons une version noncommutative de ces notions, qui pourrait conduire à une preuve complète. Nous montrons aussi une relation avec des cartes planaires pointées.
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 ..."
Abstract

Cited by 1 (1 self)
 Add to MetaCart
(Show Context)
. 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...
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 ..."
Abstract

Cited by 1 (1 self)
 Add to MetaCart
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...
Extensional Uniformity for Boolean Circuits
, 2008
"... 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 ..."
Abstract

Cited by 1 (1 self)
 Add to MetaCart
(Show Context)
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.
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 ..."
Abstract

Cited by 1 (1 self)
 Add to MetaCart
(Show Context)
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].
View update translation for XML
 in "14th International Conference on Database Theory (ICDT
"... We study the problem of update translation for views on XML documents. More precisely, given an XML view definition and a user defined view update program, find a source update program that translates the view update without side effects on the view. Additionally, we require the translation to be de ..."
Abstract

Cited by 1 (0 self)
 Add to MetaCart
(Show Context)
We study the problem of update translation for views on XML documents. More precisely, given an XML view definition and a user defined view update program, find a source update program that translates the view update without side effects on the view. Additionally, we require the translation to be defined on all possible source documents; this corresponds to Hegner’s notion of uniform translation. The existence of such translation would allow to update XML views without the need of materialization. The class of views we consider can remove parts of the document and rename nodes. Our update programs define the simultaneous application of a collection of atomic update operations among insertion/deletion of a subtree and node renaming. Such update programs are compatible with the XQuery Update Facility (XQUF) snapshot semantics. Both views and update programs are represented by recognizable tree languages. We present as a proof of concept a small fragment of XQUF that can be expressed by our update programs, thus allows for update propagation. Two settings for the update problem are studied: without source constraints, where all source updates are allowed, and with source constraints, where there is a restricted set of authorized source updates. Using tree automata techniques, we establish that without constraints, all view updates are uniformly translatable and the translation is tractable. In presence of constraints, not all view updates are uniformly translatable. However, we introduce a reasonable restriction on update programs for which uniform translation with constraints becomes possible. All authors are members of MOSTRARE, joint team of