Regular hedge model checking

We extend the regular model checking framework so that it can handle systems with arbitrary width tree-like structures. Con gurations of a system are represented by trees of arbitrary arities, sets of con gurations are represented by regular hedge automata, and the dynamics of a system is modeled by a regular hedge transducer. We consider the problem of computing the transitive closure T + of a regular hedge transducer T. This construction is not possible in general. Therefore, we present a general acceleration technique for computing T+. Our method consists of enhancing the termination of the iterative computation of the different compositions Ti by merging the states of the hedge transducers according to an appropriate equivalence relation that preserves the traces of the transducers. We provide a methodology for effectively deriving equivalence relations that are appropriate. We have successfully applied our technique to compute transitive closures for some mutual exclusion protocols de ned on arbitrary width tree topologies, as well as for an XML application.4th IFIP International Conference on Theoretical Computer ScienceRed de Universidades con Carreras en Informática (RedUNCI

LTL Model-Checking for Dynamic Pushdown Networks Communicating via Locks

A Dynamic Pushdown Network (DPN) is a set of pushdown systems (PDSs) where each process can dynamically create new instances of PDSs. DPNs are a natural model of multi-threaded programs with (possibly recursive) procedure calls and thread creation. Extension of DPNs with locks allows processes to synchronize via locks. Thus, DPNs with locks are a well adapted formalism to model multi-threaded programs that synchronize via locks. Therefore, it is important to have model-checking algorithms for DPNs with locks. However, in general, the model-checking problem of DPNs with locks against reachability properties, and hence Linear Temporal Logic (LTL), is undecidable. To obtain de-cidable results, we study in this work the model-checking problem of DPNs with well-nested locks against single-indexed Linear Temporal Logic (LTL) properties of the form E f i s.t. f i is a LTL formula interpreted over the PDS i. We show that this model-checking problem is decidable. We propose an automata-based approach for computing the set of configurations of a DPN with locks that satisfy the corresponding single-indexed LTL formula

Attenuation Regulation as a Term Rewriting System

The classical attenuation regulation of gene expression in bacteria is considered. We propose to represent the secondary RNA structure in the leader region of a gene or an operon by a term, and we give a probabilistic term rewriting system modeling the whole process of such a regulation.Comment: to appea

Mining Malware Specifications through Static Reachability Analysis

International audienceAbstract. The number of malicious software (malware) is growing out of control. Syntactic signature based detection cannot cope with such growth and manual construction of malware signature databases needs to be replaced by computer learning based approaches. Currently, a single modern signature capturing the semantics of a malicious behavior can be used to replace an arbitrarily large number of old-fashioned syntactical signatures. However teaching computers to learn such behaviors is a challenge. Existing work relies on dynamic analysis to extract malicious behaviors, but such technique does not guarantee the coverage of all behaviors. To sidestep this limitation we show how to learn malware signatures using static reachability analysis. The idea is to model binary programs using pushdown systems (that can be used to model the stack operations occurring during the binary code execution), use reachability analysis to extract behaviors in the form of trees, and use subtrees that are common among the trees extracted from a training set of malware files as signatures. To detect malware we propose to use a tree automaton to compactly store malicious behavior trees and check if any of the subtrees extracted from the file under analysis is malicious. Experimental data shows that our approach can be used to learn signatures from a training set of malware files and use them to detect a test set of malware that is 5 times the size of the training set

Dividendes En Présence Des Imperfections Du Marché

The topic of the company's dividend policy has captured the interest of economists and over the last five decades has been the subject of several theoretical and empirical studies. Economists have proposed a number of theories to explain the dividend puzzle. The purpose of this paper is to examine the effect of market imperfections (asymmetric information, agency costs and the impact of taxation) on corporate dividend policy. While briefly presenting the main theories of dividend policy and summarizing the empirical evidence on these theories. The paper reaches at a conclusion that the famous dividend puzzle is still unresolved. The empirical evidence is ambiguous and the search for a new explanation of dividends is continuing

SPADE: Verification of Multithreaded Dynamic and Recursive Programs

International audienceThe tool SPADE allows to analyse automatically boolean programs with parallelism, communication between parallel processes, dynamic process creation, and recursion at the same time. As far as we know, this is the first software model checking tool based on an expressive model that accurately models all these aspects in programs

Dividend Pay-out Policy and Share Price: A Atudy of Listed Firms in Morocco

The main purpose of this study is to examine the relationship between dividend policy and financial performance in Morocco stock market. The panel data regression method is used to analyze the relationship of share price with dividend per share. This study presumes that dividend policy has an effect on the share price in Morocco. Also, it assumes that companies that pay dividends tend to have a higher financial performance than those that do not. On the other hand, companies that do not distribute dividends are more indebted and have a smaller size compared to distributors. The results of the econometric analysis conducted indicate that the dividends distributed and the profits are found to be significantly positive for the financial performance of Moroccan companies

Dividend Pay-out Policy and Share Price: A Study of Listed Firms in Morocco

The main purpose of this study is to examine the relationship between dividend policy and financial performance in Morocco stock market. The panel data regression method is used to analyze the relationship of share price with dividend per share. This study presumes that dividend policy has an effect on the share price in Morocco. Also, it assumes that companies that pay dividends tend to have a higher financial performance than those that do not. On the other hand, companies that do not distribute dividends are more indebted and have a smaller size compared to distributors. The results of the econometric analysis conducted indicate that the dividends distributed and the profits are found to be significantly positive for the financial performance of Moroccan companies