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Loudini M.,Laboratoire Of Communication Dans Les Systemes Informatiques Lcsi | Rezig S.,Laboratoire Of Communication Dans Les Systemes Informatiques Lcsi
International Journal of Web Engineering and Technology | Year: 2013

This article addresses an investigation of the capabilities of intelligent feedback control methodologies to provide satisfactory web server quality of service (QoS) in terms of delay services. Fuzzy logic-based control architectures are proposed to enhance the system performances. The first closed-loop control scheme to be applied is the standard proportional integral (PI) type Mamdani's fuzzy logic controller (FLC). Then, the simulated annealing (SA) algorithm (SAA) is used to optimise the FLC parameters with innovative tuning procedures. Both of the FLC and the SA optimised FLC (SAOFLC) are implemented and tested to attempt to improve the QoS of a web server faced to sudden variations of workload. The performances of the adopted closed-loop intelligent control strategies are examined via simulation experiments. Copyright © 2013 Inderscience Enterprises Ltd. Source


Badaoui A.,University of Boumerdes | Loudini M.,Laboratoire Of Communication Dans Les Systemes Informatiques Lcsi | Hidouci W.-K.,Laboratoire Of Communication Dans Les Systemes Informatiques Lcsi
Proceedings of the 10th International Symposium on Programming and Systems, ISPS' 2011 | Year: 2011

Performance modeling is an important topic in overload control for web servers. Several attempts have been made to create performance models for web servers. The paper describes modeling a Web server to be controlled by Feedback control scheme. Feedback command theory was initially used to control of industrial processes. Its use for the control of performance software is recent. It provides a number of mathematical tools which can be used to analyze the stability of the commanded system and find the best adjustment that responds to the performance criteria. Our approach proceeds in two steps: system identification and controller design. In system identification, we construct mathematical models of the target system in forms of discrete transfer function focused on single-input single-output (SISO) systems. The role of controller is to modify the transfer function of the target system with regard to the control error between the reference value and the output value. © 2011 IEEE. Source


Bennama M.,Laboratoire Of Communication Dans Les Systemes Informatiques Lcsi | Bouabana-Tebibel T.,Laboratoire Of Communication Dans Les Systemes Informatiques Lcsi
CEUR Workshop Proceedings | Year: 2014

The UML (Unified Modeling Language) graphical models miss providing some pertinent elements of specification as constraints over objects and operations. To fill this lack, OCL (Object Constraint Language) has been developed by IBM and integrated to UML as a modern and formal modeling language, which is easy to learn and efficient to use. On the other hand, many works emerged providing a formal semantics to UML dynamic diagrams by using CP-nets (High-level Petri Nets). The latter are verified based on system properties written in temporal logic. The purpose of this paper is to assist the UML modeler, not necessarily familiar with temporal logics, by letting him expressing the properties in OCL language and proposing an automatic mapping of OCL invariants and pre/post-conditions into CTL-like logic (Computational Tree Logic) coupled with the functional programming language Standard ML. The obtained temporal logic formulas are verified over the state space of the CP-net models derived from UML diagrams by model-checking. Source


Bouabana-Tebibel T.,Laboratoire Of Communication Dans Les Systemes Informatiques Lcsi | Rubin S.H.,Systems Center Pacific | Habib K.,Laboratoire Of Communication Dans Les Systemes Informatiques Lcsi | Chebba A.,Laboratoire Of Communication Dans Les Systemes Informatiques Lcsi | And 2 more authors.
Advances in Intelligent Systems and Computing | Year: 2014

The modeling and design of complex systems continues to face grand challenges in feedback and control. Existing languages and tools, either textual or graphical, bring some improvement for such purposes, but much remains to be done in order to readily insure scalability. In this chapter, we propose a language which gathers specialization and composition properties. It is our belief that the latter properties bear the necessary capabilities to overcome the difficulties raised when developing these systems. The language is designed in a way to be specific to complex system domains. It supports a component-based structure that conforms to a user-friendly component assembly. The proposed structure is based on static, dynamic, functional and parametric parts. It is conceived in the spirit of SysML concepts. The language also supports textual and graphical specification. The specified models generate Internal Block Diagrams. A modeling tool is built on the basis of the Eclipse framework. © Springer International Publishing Switzerland 2014. Source


Kaci A.,Laboratoire Of Communication Dans Les Systemes Informatiques Lcsi | Bouabana-Tebibel T.,Laboratoire Of Communication Dans Les Systemes Informatiques Lcsi | Challal Z.,Laboratoire Of Communication Dans Les Systemes Informatiques Lcsi
Proceedings of the 2014 International Conference on Advances in Computing, Communications and Informatics, ICACCI 2014 | Year: 2014

The current trend towards outsourcing data to the Cloud Computing requires rigorous techniques to deal with data confidentiality. Encryption is one of the most secure techniques in use. However, it remains weak against some indiscretions, and presents incompleteness in the measures offered to ensure confidentiality. New flaws appear, inducing confidential information disclosure, despite a secure and rigorous data encryption. In this article, we propose to enhance the level of confidentiality that may already be guaranteed for outsourced data. We are particularly interested in access control on the result of the search over encrypted data. The property behind this aspect of security is known as ACAS (Access Control Aware Search) principle. We present an approach which integrates the access control mechanism with data encryption in order to comply with ACAS. The used techniques are based on Searchable Encryption and Attribute Based Encryption methods. The proposed model has been evaluated based on data size and access control complexity. © 2014 IEEE. Source

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