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Cloud computing is gaining an increasing popularity and the number of user's applications and interactions with Cloud resources have grown considerably making Cloud services more susceptible to failure. Therefore, fault tolerance is... more
Cloud computing is gaining an increasing popularity and the number of user's applications and interactions with Cloud resources have grown considerably making Cloud services more susceptible to failure. Therefore, fault tolerance is an important property in order to achieve reliability, availability and required quality of service. Several studies were interested in Cloud fault tolerance issues. These studies proposed solutions including checkpoint and replication that are focused on failure of a single Cloud resource, namely virtual machines, and virtualization issues. Such solutions are insufficient given Cloud complexity. Unlike previous work, we propose a solution that takes into consideration not only virtual machines but also physical machines. Our solution is a hybrid fault tolerance strategy that inherits good features and overcome the limitations of traditional fault tolerance strategies. We evaluate the efficiency of our fault tolerance strategy compared to replication and checkpoint strategies by using CloudSim and we prove that our strategy leads to better results.
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A Web service (WS) is called compound or composite when its execution involves interactions with other WS to use their features. The composition of WS specifies which services need to be invoked, in what order and how to handle exception... more
A Web service (WS) is called compound or composite when its execution involves interactions with other WS to use their features. The composition of WS specifies which services need to be invoked, in what order and how to handle exception conditions. This paper gives an overview of research efforts of WS composition. The approaches proposed in the literature are diverse, interesting and have opened important research areas. Based on many studies, we extracted the most important role of WS composition use in order to facilitate its introduction in WS concept.
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Cloud computing including hardware, software and networks are growing towards an ever increasing scale and heterogeneity, becoming overly complex. In order to manage such growing complexity and information overload, nowadays Cloud... more
Cloud computing including hardware, software and networks are growing towards an ever increasing scale and heterogeneity, becoming overly complex. In order to manage such growing complexity and information overload, nowadays Cloud researchers propose to enrich the Cloud with Autonomic Computing properties. In fact the autonomic computing focuses on self-adaptable computing systems to the maximum extent possible without human intervention or guidance. The Cloud Infrastructure is partially automated. This limitation results from the absence of an architectural model for describing distributed resources and their interdependencies in terms of configuration. This article proposes a model of distributed resources in the form of a set of resources interconnected and automated in order to predict and configure cloud resources. We propose to use the agent technology in order to provide a distributed solution for the decentralized resources self-configuring and the adaptation of the Cloud infrastructure. We enhanced the proposed model with neural prediction method and broker agent in order to ameliorate the performance of the Cloud Infrastructure. Moreover, the proposed model has been validated using a formal policy.
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Tuning the parameters of any evolutionary algorithm is considered as a very difficult task. In this paper, we present a new adaptive multi-objective technique which consists of a hybridization between a particular particle swarm... more
Tuning the parameters of any evolutionary algorithm is considered as a very difficult task. In this paper, we present a new adaptive multi-objective technique which consists of a hybridization between a particular particle swarm optimization approach (Tribes) and tabu search (TS) technique. The main idea behind this hybridization is to combine the rapid convergence of Tribes with the high efficient exploitation of a local search technique based on TS. In addition, we propose three different places where the local search can be applied: TS applied on the particles of the archive, TS applied only on the best particle of each tribe and TS applied on each particle of the swarm. The aim of those propositions is to study the impact of the place where the local search is applied on the performance of our hybridized Tribes. The mechanisms proposed are validated using 10 different functions from specialized literature of multi-objective optimization. The obtained results show that using this kind of hybridization is justified as it is able to improve the quality of the solutions in the majority of cases.
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The key difference of Vehicular Ad- hoc Network (VANET) and Mobile Ad-hoc Network (MANET) is the exceptional mobility pattern and quick variability variable of network topology. The existing MANET routing protocols are inadequate for the... more
The key difference of Vehicular Ad- hoc Network (VANET) and Mobile Ad-hoc Network (MANET) is the exceptional mobility pattern and quick variability variable of network topology. The existing MANET routing protocols are inadequate for the VANET. One good manner of data sending in vehicular environment is to enhance the MANET routing protocols and make them appropriate for the VANET. Ad-hoc On-demand Distance Vector (AODV) is one of the most important MANET reactive protocols. Nevertheless, once we have to deal with a VANET, its performance is poor. In this paper, we propose an enhancing the AODV routing protocol based on agent technology to improve the Quality of Service (QoS) in VANET. The experimental results show that our approach outperforms the AODV protocol in terms of routing overhead, dropped packets rate and transfer packets delay.
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Research Interests: Computer Science, Distributed Computing, Artificial Intelligence, Evolutionary Computation, Face Recognition, and 15 moreFace Detection, CAM, Engineering Systems, Edge Detection, Image recognition, Evolutionary Computing, Evolutionary Algorithm, Hybrid Algorithm, DDC, Evolutionary optimization, B spline, Artificial Neural Network, General Population, Feed Forward Neural Network, and Firing pattern
OPT-D3 G2 A: un nouvel Algorithme Genetique Distribue Doublement Guide pour les CSOPs Bouamama Sadok & Khaled Ghedira SOIE/Universite Tunis Sadok.Bouamama@ensi.rnu.tn khaled.ghedira@isg.rnu.tn Resume Les problemes de satisfaction de... more
OPT-D3 G2 A: un nouvel Algorithme Genetique Distribue Doublement Guide pour les CSOPs Bouamama Sadok & Khaled Ghedira SOIE/Universite Tunis Sadok.Bouamama@ensi.rnu.tn khaled.ghedira@isg.rnu.tn Resume Les problemes de satisfaction de contraintes (CSPs) sont au cœur de nombreuses applications en intelligence artificielle. Les CSOP sont une extension des CSP. L’approche proposee dans ce papier s’attaque a la resolution des CSOPs. Notre approche est une Approche hybride des algorithmes genetiques, qui profite a fond des avantages des systemes multi- agents pour pallier la complexite temporelle des algorithmes genetiques. Ladite approche est guidee par l’heuristique de minimisation des conflits et par le concept des « templates ». Dans ce papier on presentera la nouvelle approche ainsi que les resultats experimentaux. 1. Introduction Les problemes de satisfaction de contraintes (CSP) sont au cœur de nombreuses applications en intelligence artificielle et recherche operationnelle, telles que l'allocation de ressources, la planification, l'ordonnancement. Un probleme de satisfaction de contraintes ou CSP, P = (X, D, C) est defini par : - X est un ensem
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Mobile agent technologies are known for their capacity to develop and construct distributed, heterogeneous and interoperable systems. Despite the presence of several platforms for the development of mobile agent applications, security... more
Mobile agent technologies are known for their capacity to develop and construct distributed, heterogeneous and interoperable systems. Despite the presence of several platforms for the development of mobile agent applications, security issues act as a main deterrent against such trends. Based on this, we conducted a comparative study of the most promising and existing mobile agent platforms, showing the diverse security features employed to address various threats. We investigate also the trust models used by the platforms. The established study focuses on the contributions to verify security criteria by the used security mechanisms in every studied platform. This study is important not only to allow practitioners pick the most suitable platforms to meet their security requirements, but also to allow researchers address the voids by ameliorating the concluded limits and proposing possible improvements of new versions of these platforms.
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A cloud provider provides, on-demand, physical computing resources to clients. It enables clients to improve their computing delivered resources in virtual machines. However, the cloud provider faces major problems impacting its correct... more
A cloud provider provides, on-demand, physical computing resources to clients. It enables clients to improve their computing delivered resources in virtual machines. However, the cloud provider faces major problems impacting its correct operation. One of these problems is that a cloud provider cannot deliver more resources when it has not enough resources during peak hours. Another problem related to providers is their inability to satisfy all client's requirements. In order to increase the reliability and the availability of cloud providers resources, we have proposed a distributed approach based on Contract Net Protocol (CNP) to overcome the limited resources problem. We have proposed also an extension for Open Virtualization Format (OVF) standard to describe resources provisioning in cloud federation. This extension includes more information about the client, the provider identification and the quality of service. To prove the efficiency and the effectiveness of our approach, we have suggested a real case study illustrating how a client can interact with our approach for the provision of two-tier web application. In addition to that, we have implemented a prototype to evaluate the key idea presented in this paper through a set of experiments.
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The rapid growth of published Web services (WS) makes their discovery more difficult. There are many WS that have similar functional characteristics. So, it is obligatory to facilitate to consumers the selection of the most relevant WS... more
The rapid growth of published Web services (WS) makes their discovery more difficult. There are many WS that have similar functional characteristics. So, it is obligatory to facilitate to consumers the selection of the most relevant WS according to their needs. Different approaches have been proposed to WS discovery including syntactic, semantic and context aware approaches. In this paper, we highlight the importance of behavioral aspect in WS discovery. We argue that the execution manner of WS operations become a quality criterion which has not been treated in the previously proposed approaches. The purpose of this paper is to realize a literature review of existing research on WS discovery and highlight their failure to deal with the behavioral aspect.
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Particle Swarm Optimization (PSO) algorithm is a metaheuristic. This method has been used for solving optimization problems. As many other metaheuristics, several modifications in this method have been carried out in order to improve the... more
Particle Swarm Optimization (PSO) algorithm is a metaheuristic. This method has been used for solving optimization problems. As many other metaheuristics, several modifications in this method have been carried out in order to improve the performance of the search. Island models is a structured population mechanism used in evolutionary algorithms to preserve the population diversity and thus to improve their performances. In this paper, the island model concepts are embedded into the PSO algorithm to improve its diversity as well as its convergence, where the new method is referred to as island-PSO. In this approach, the particles are distrusted into separate sub-swarm named (islands). After specific generations, a number of particles run an exchange through a migration process. This process is performed to keep the diversity into the PSO algorithm and to allow the islands to interact with each other. The experimental results using a set of benchmark functions show that the island model context is crucial to the PSO performance and the comparative study shows the efficiency of using island models.
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The multimodal transport is a solution adopted by the governments to solve many challenges like the energy consumption and the pollution. Actually, the multimodal transport faces many problems as those related to the distribution, the... more
The multimodal transport is a solution adopted by the governments to solve many challenges like the energy consumption and the pollution. Actually, the multimodal transport faces many problems as those related to the distribution, the focus of many researchers who have classified it as a NP-hard problem. The goal of this work is to develop a distributed guided genetic algorithm to solve the problem of multimodal transport, specially the disturbance. The solution must be valid in the normal case and in the degraded mode. So, this study aims to improve the quality of services offered to users. In fact, our approach is based on evolutionary algorithms, and more precisely on the genetic algorithm. We use hybridization in the selection operator and integration of a new structure in the mutation operator which supports on a multi-criteria method for the detection of itineraries.
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In the literature, several studies have shown that the use of trust models in mobile agent-based systems has advantages for improving the level of security and performance. This paper presents a comparative study of trust models specific... more
In the literature, several studies have shown that the use of trust models in mobile agent-based systems has advantages for improving the level of security and performance. This paper presents a comparative study of trust models specific to mobile agents, showing their strengths and limitations. The comparison is made based on several dimensions. The purpose of this study is to analyze the used dimensions by these models (parameters, concepts, etc.) and to identify the dimensions that are not used in the existing models of trust. This study will allow researchers to address the voids by ameliorating the concluded limits and proposing a new trust model, which besides incent entities to not adopt a selfish and/or strategic behavior will reflect better the reality of the behavior of the different entities on the mobile agent system. As a result, the trust values will be more accurate and the decision-making will be more precise. To make the requirements of the trust model easier to understand, we add a B2B application based on mobile agents and we integrate into each host of it a trust layer that allows the integration of the proposed dimensions. We present also the flowchart of the new related trust model.
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The increasing crisis frequency and the growing impact of their damages require efficient crisis management processes in order to manage crisis effectively and reduce losses. In such context, the need of accurate and updated information... more
The increasing crisis frequency and the growing impact of their damages require efficient crisis management processes in order to manage crisis effectively and reduce losses. In such context, the need of accurate and updated information about crises is extremely important. In recent years, crisis information has frequently been provided by social media platforms such as Twitter, Facebook, Flickr, etc. In fact, considering the huge amount of shared information, their precision and their real time characteristic, organizations are moving towards the development of crisis management applications that include information provided by social media platforms. Following this view, the main purpose of our work is to propose a framework for Tunisian tweets extraction and analysis. More precisely, we provide an architecture that includes necessary components and tools for Tunisian dialect treatment. The proposed architecture is an extension on the existing AIDR platform. In addition, we specify the functioning of the proposed architecture to enable firstly terms transliteration from Arabic to Latin alphabet, secondly their normalization and finally their translation in order to be treated by existing social media analysis platform.
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Recently, the number of Android apps has witnessed an ever-increase that is becoming a ubiquitous presence in our daily lives. These apps are evolving fast by offering new characteristics and functionalities. These ongoing improvements... more
Recently, the number of Android apps has witnessed an ever-increase that is becoming a ubiquitous presence in our daily lives. These apps are evolving fast by offering new characteristics and functionalities. These ongoing improvements often affect app quality due to bad design practices and poor coding, known as Android code smells. In this context, the recent works highlighted the importance of the design quality of mobile application. To this end, many methods and tools are proposed to assess the quality of graphical user interface (GUI) and source code of Android apps, such as heuristic evaluation and field-testing, etc. In addition, the features and design of these Android apps may introduce bad design practices, that can highly decrease the quality and the performance of these Android applications. In this paper, we empirically study the diffuseness of GUI aesthetic defects and the code smells of the presentation layer of Android apps. Then, we investigate the impact of the appearance of code smells on the aesthetic of Android apps. To this end, we use two evaluation tools. The first one is called PLAIN which consists of detecting aesthetic defects by measuring a set of structural metrics of GUI. The second one is Android UI Detector which aims to identify the presentation layer code smells of Android apps. This analysis study is based on 8480 GUIs of 120 Android apps. The obtained results confirm that code smells of the presentation layer of Android apps have an impact on GUI aesthetic defects.
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In this article, we propose an improvement of the Available-To-Promise (ATP) function which constitutes one of the important functions within the enterprise and the Supply Chain. The basic role of this function is to response to customer... more
In this article, we propose an improvement of the Available-To-Promise (ATP) function which constitutes one of the important functions within the enterprise and the Supply Chain. The basic role of this function is to response to customer requests on the products' availability. The proposed approach supports the dynamic and moving environment and handles with a variable demand. Its goal is to give an immediate response to the customers, to privilege the rush orders and to minimize the number of backorders. Our approach is based on the current orders to estimate the future demand and to establish a new ATP function called efficient ATP. In case of shortages, our approach uses cooperation between the different entities of the supply chain to fulfill the customer requirements. Experimentations have been achieved and showed the effectiveness of our approach.
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Software refactoring aims at optimizing software modularization by improving internal software structure without altering its external behavior. There exists various approaches for suggesting refactoring opportunities, based on different... more
Software refactoring aims at optimizing software modularization by improving internal software structure without altering its external behavior. There exists various approaches for suggesting refactoring opportunities, based on different sources of information, e.g., structural, semantic, and historical. In this paper, we propose a data fusion model to combine different sources of information in order to identify refactoring opportunities and we instantiate it to support Move Class refactoring. We report the results of our validation conducted on four software systems and we show that our proposal improves the modularization quality by 29% and that our tool is able to provide meaningful recommendations for move class refactoring. Specifically, more than 70% of the recommendations were considered meaningful from the developers' point of view.
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Many real-world optimization problems evolve in a dynamically changing environment: the problem to solve changes through time, and no information about changes and problem evolution is available ahead of time. When solving such problems,... more
Many real-world optimization problems evolve in a dynamically changing environment: the problem to solve changes through time, and no information about changes and problem evolution is available ahead of time. When solving such problems, we need an optimization technique which is able not only to converge around optimal solutions but also to follow their shifting through time as closely as possible. In this paper, we propose a new ACO (Ant Colony Optimization) approach for solving dynamic problems. Like in PACO, every time the problem changes, instead of restarting from scratch, pheromone trails are re-computed at each time w.r.t a set of already found solutions. However, in order to avoid the algorithm to be misguided, the new pheromone trails are first tested. The goal is to study the relevancy of the re-computed pheromone trails w.r.t the changes and consequently to adjust/correct their values. The proposed algorithm is tested on Dynamic TSP (Traveling Salesman Problem) instances.
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This paper deals with the problem of optimally regulating planned vehicle timetables for public transport when unforeseen events occur in real-time in the network. A multicriteria problem is solved...