Results 1  10
of
30
Polynomial closure and unambiguous product
 Theory Comput. Systems
, 1997
"... This paper is a contribution to the algebraic theory of recognizable languages. The main topic of this paper is the polynomial closure, an operation that mixes together the operations of union and concatenation. Formally, the polynomial closure of a class of languages L of A ∗ is the set of language ..."
Abstract

Cited by 32 (5 self)
 Add to MetaCart
This paper is a contribution to the algebraic theory of recognizable languages. The main topic of this paper is the polynomial closure, an operation that mixes together the operations of union and concatenation. Formally, the polynomial closure of a class of languages L of A ∗ is the set of languages
Execution monitoring enforcement under memorylimitation constraints
 Information and Computation
"... Abstract. Recently, attention has been given to formally characterize security policies that are enforceable by different kinds of security mechanisms. A very important research problem is the characterization of security policies that are enforceable by execution monitors constrained by memory limi ..."
Abstract

Cited by 9 (0 self)
 Add to MetaCart
Abstract. Recently, attention has been given to formally characterize security policies that are enforceable by different kinds of security mechanisms. A very important research problem is the characterization of security policies that are enforceable by execution monitors constrained by memory limitations. This paper contributes to give more precise answers to this research problem. To represent execution monitors constrained by memory limitations, we introduce a new class of automata, Bounded History Automata. Characterizing memory limitations leads us to define a precise taxonomy of security policies that are enforceable under memory limitation constraints.
Degrees of Lookahead in Regular Infinite Games
"... Abstract. We study variants of regular infinite games where the strict alternation of moves between the two players is subject to modifications. The second player may postpone a move for a finite number of steps, or, in other words, exploit in his strategy some lookahead on the moves of the opponent ..."
Abstract

Cited by 5 (0 self)
 Add to MetaCart
Abstract. We study variants of regular infinite games where the strict alternation of moves between the two players is subject to modifications. The second player may postpone a move for a finite number of steps, or, in other words, exploit in his strategy some lookahead on the moves of the opponent. This captures situations in distributed systems, e.g. when buffers are present in communication or when signal transmission between components is deferred. We distinguish strategies with different degrees of lookahead, among them being the continuous and the bounded lookahead strategies. In the first case the lookahead is of finite possibly unbounded size, whereas in the second case it is of bounded size. We show that for regular infinite games the solvability by continuous strategies is decidable, and that a continuous strategy can always be reduced to one of bounded lookahead. Moreover, this lookahead is at most doubly exponential in the size of the parity automaton recognizing the winning condition. We also show that the result fails for nonregular games where the winning condition is given by a contextfree ωlanguage. 1
The Expressive Power of Existential First Order Sentences of Büchi's Sequential Calculus
"... this paper is to study the first order theory of the successor, interpreted on finite words. More specifically, we complete the study of the hierarchy based on quantifier alternations (or \Sigma nhierarchy). It was known (Thomas, 1982) that this hierarchy collapses at level 2, but the expressive po ..."
Abstract

Cited by 5 (1 self)
 Add to MetaCart
this paper is to study the first order theory of the successor, interpreted on finite words. More specifically, we complete the study of the hierarchy based on quantifier alternations (or \Sigma nhierarchy). It was known (Thomas, 1982) that this hierarchy collapses at level 2, but the expressive power of the lower levels was not characterized effectively. We give a semigroup theoretic description of the expressive power of \Sigma 1 , the existential formulas, and B\Sigma 1 , the boolean combinations of existential formulas. Our characterization is algebraic and makes use of the syntactic semigroup, but contrary to a number of results in this field, is not in the scope of Eilenberg's variety theorem, since B\Sigma 1 definable languages are not closed under residuals
The expressive power of existential firstorder sentences of Büchi's sequential calculus
"... The aim of this paper is to study the rstorder theory of the successor, interpreted on nite words. More speci cally, we are interested in the hierarchy based on quanti er alternations (or n hierarchy). It was known (Thomas, 1982) that this hierarchy collapses at level 2, but the expressive po ..."
Abstract

Cited by 4 (0 self)
 Add to MetaCart
The aim of this paper is to study the rstorder theory of the successor, interpreted on nite words. More speci cally, we are interested in the hierarchy based on quanti er alternations (or n hierarchy). It was known (Thomas, 1982) that this hierarchy collapses at level 2, but the expressive power of the lower levels was not characterized eectively. We give a semigroup theoretic description of the expressive power of B 1 , the boolean combinations of existential formulas. We also give an O(n ) time algorithm to decide whether the language accepted by a deterministic nstate automaton is expressible by a rst order sentence (respectively a B 1 sentence).
An Algorithm To Verify Local Threshold Testability Of Deterministic Finite Automata
 Lecture Notes in Computer Science
, 1999
"... A locally threshold testable language L is a language with the property that for some nonnegative integers k and l, whether or not a word u is in the language L depends on (1) the prefix and suffix of the word u of length k \Gamma 1 and (2) the set of intermediate substrings of length k of the word ..."
Abstract

Cited by 4 (1 self)
 Add to MetaCart
A locally threshold testable language L is a language with the property that for some nonnegative integers k and l, whether or not a word u is in the language L depends on (1) the prefix and suffix of the word u of length k \Gamma 1 and (2) the set of intermediate substrings of length k of the word u where the sets of substrings occurring at least j times are the same, for j l. For given k and l the language is called lthreshold ktestable. A finite deterministic automaton is called lthreshold ktestable if the automaton accepts a lthreshold ktestable language. In this paper, the necessary and sufficient conditions for an automaton to be locally threshold testable are found. We introduce the first polynomial time algorithm to verify local threshold testability of the automaton based on this characterization.
Generalized Deterministic Languages and their Automata: A Characterization of Restricted Temporal Logic
 INST. FUR INFORMATIK, UNIV. WURZBURG
, 1999
"... Let TL[X; F] (TL[F]) be the class of formulas of temporal logic, where as the only temporal operators X (next) and F (eventually) are allowed (only F is allowed, resp.). For a class \Phi ` TL[X; F] let L(\Phi) be the class of \Phidefinable languages. Among others, characterizations of L(TL[X; F]) ..."
Abstract

Cited by 4 (1 self)
 Add to MetaCart
Let TL[X; F] (TL[F]) be the class of formulas of temporal logic, where as the only temporal operators X (next) and F (eventually) are allowed (only F is allowed, resp.). For a class \Phi ` TL[X; F] let L(\Phi) be the class of \Phidefinable languages. Among others, characterizations of L(TL[X; F]) and L(TL[F]) in terms of forbidden patterns in finite automata are known. Here we ask for every bound k 0 on the number of nested uses of the next operator for the expressive power of the respective fragment of TL[X; F]. Denote by TL[X(k); F] the class of formulas in TL[X; F] with nesting depth k in the next operator. Obviously, L(TL[X; F]) = S k0 L(TL[X(k); F]) and L(TL[F]) = L(TL[X(0); F]). We prove a levelwise characterization of the above syntactical hierarchy (1) in terms of a certain pattern S rev k (cf. Figure 6) that must not appear in the transition graph of deterministic finite automata, and (2) in terms of a formal language representation involving kleftdeterministic lan...
Positive Varieties And Infinite Words
"... Carrying on the work of Arnold, Pecuchet and Perrin, Wilke has obtained a counterpart of Eilenberg's variety theorem for finite and infinite words. In this paper, we extend this theory for classes of languages that are closed under union and intersection, but not necessarily under complemen ..."
Abstract

Cited by 3 (0 self)
 Add to MetaCart
Carrying on the work of Arnold, Pecuchet and Perrin, Wilke has obtained a counterpart of Eilenberg's variety theorem for finite and infinite words. In this paper, we extend this theory for classes of languages that are closed under union and intersection, but not necessarily under complement. As an example, we give a purely algebraic characterization of various classes of recognizable sets defined by topological properties (open, closed, F and G ) or by combinatorial properties
Hierarchies of piecewise testable languages, a version containing also Appendix, http://www.math.muni.cz/~polak
"... Abstract. The classes of languages which are boolean combinations of languages of the form A ∗ a1A ∗ a2A ∗... A ∗ aℓA ∗ , where a1,..., aℓ ∈ A, ℓ ≤ k, for a fixed k ≥ 0, form a natural hierarchy within piecewise testable languages and have been studied in papers by Simon, BlanchetSadri, Volkov and ..."
Abstract

Cited by 2 (2 self)
 Add to MetaCart
Abstract. The classes of languages which are boolean combinations of languages of the form A ∗ a1A ∗ a2A ∗... A ∗ aℓA ∗ , where a1,..., aℓ ∈ A, ℓ ≤ k, for a fixed k ≥ 0, form a natural hierarchy within piecewise testable languages and have been studied in papers by Simon, BlanchetSadri, Volkov and others. The main issues were the existence of finite bases of identities for the corresponding pseudovarieties of monoids and generating monoids for these pseudovarieties. Here we deal with similar questions concerning the finite unions and positive boolean combinations of the languages of the form above. In the first case the corresponding pseudovarieties are given by a single identity, in the second case there are finite bases for k equal to 1 and 2 and there is no finite basis for k ≥ 4 (the case k = 3 remains open). All the pseudovarieties are generated by a single algebraic structure.