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International Journal of Computer Applications (0975 - 8887) Volume 28- No.

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International Journal of Computer Applications (0975 – 8887) Volume 28– No. 9 , August 2011 21 New Approach Timer for the Control of the Distributed Systems with the Multi-Agents Systems Saqalli Meryem Computer Science System Architecture Team, Computing, Systems and Renewable Energy Laboratory Medromi Hicham Computer Science System Architecture Team, Computing, Systems and Renewable Energy Laboratory ABSTRACT The real-time computing is widely used and gets more and more importance in the everyday life. Several fields of application are concerned, in particular, the automobile, the avionics, the multimedia, the energy, etc. The real-time systems concern IT applications having a role of follow-up or control of process in an environment which evolves dynamically. In this article we propose a new approach called "Timer" for the distributed multi- agents architectures. This approach is validated and implemented on the platform of security and detection of intrusion. The objective of this Timer approach is to verify the capacity of every agent to perceive its environment and to elaborate an answer in the required time. General Terms Internet and Distributed Computer Systems. Keywords Platform, Distributed System, Multi-Agents Systems, Real Time System. Control. 1. INTRODUCTION The real-time systems are more and more present in the everyday life, we find them in the aeronautics, the railroad transport, the automobile, the household electrical appliances or the multimedia. We indicate by real time, any application implementing a computer system the behavior (functioning) is conditioned by the dynamic evolution of the state of an environment (called proceeded). The role of the computer system is to follow or to monitor this process by respecting temporal constraints predefined in the specifications of the application. Also, we qualify in the real time any computer system which has the correction of the functioning which depends not only on the logical exactness of the results which it supplies, but especially depends on the date in which these results are produced. So, the system does not treat any more only values, but valuable couples values and time. This definition implies that the only average speed of execution of the software does not accept the validity of the system, but temporal constraints must be respected (by examples the terms of treatments are relative to a measurable physical time and are a member (part) of the specification of the implanted system) [1]. 2. MULTI-AGENT APPROACH 2.1 Agent An agent is an autonomous and intelligent, real or abstract entity, who is capable of acting on itself and on her environment in a multi-universe agent also, she can communicate with the other agents and whose behavior is the consequence of her observations, her knowledge and the interactions with the other agents [2]. 2.2 Multi-Agent System A multi-system agent is a compound distributed system of a set of agents, who feign to a certain extent the capacities of the human reasoning, the SMA is ideally conceived and implemented as a set of agents interacting between each other (Fig.1 [3]), mostly, according to modes of cooperation, competition or coexistence. A system multi-agent can be: Opened: the agents enter it and go out of it freely. (An example of that is in e-commerce). Closed: group agents stay the same. (A football match is an example). Homogeneous: all the agents are built on the same model. (A working meeting, a colony of ants). Heterogeneous: agents of different models, granularities different. (An ecosystem). Mixed (or not): the agents "human beings" are integral part of the system. It is opened and heterogeneous. (A Medie workgroup by agents assistants) [4]. Fig1: Principle of a Multi agents System 3. REAL TIME SYSTEM The systems agent times realities are defined by their capacity to react constantly to the requests of their environment by
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International Journal of Computer Applications (0975 – 8887) Volume 28– No. 9 , August 2011 22 conforming to a certain number of temporal constraints. At limited time, the system has to acquire and treats the data and the events characterizing the temporal evolution of this environment, to make the appropriate decisions and to transform them into actions. The feature of the system results from its capacity to present the good exits (logical correction) at the right time (temporal correction). Because of the often critical character of this type of applications, the corresponding software and material architectures are specified, developed, validated with the biggest care and are then congealed so as to make sure that the system that will have determinist and predictable behavior. The contribution of the multi-agents systems in this frame can then seem limited, in particular due to the autonomy and the pro-activity which we attribute generally to the agents. Actually, numerous examples of use of the multi-agents systems in a context time - reality advance more the distributed aspect than the aspects of decentralization and autonomy. It is a question of putting on together distributed entities but with motionless global architecture [5]. Fig2: Real Time System 3.1 Characteristics of the real-time systems In the context of the real-time systems, the data have a validity defined at once by the domain of accepted values and by the duration of validity of these, which depends naturally on the term. The data have duration of limited existence. Otherwise, the systems of control have to respect two functional and temporal requirements in parallel [6]. According to the temporal constraints, we distinguish two big categories of the real-time systems: - Real-time systems with strict constraints (hard real time): when all the temporal constraints must be necessarily respected [7]. The non compliance with the constraints can provoke catastrophic consequences (The systems of control of flight, systems of control of nuclear station). - Real-time systems with relative constraints (supple real time): unlike the hard systems, the non compliance with the temporal constraints is tolerated (acceptable) by the system and without that it has catastrophic consequences [8], for example multimedia applications. - Real-time systems with mixed constraints: tasks with strict constraints and tasks with relative constraints [9] consist. 3.2 Real-time Operating systems owners The purpose of this part is to make a fast survey of the main real-time operating systems: - VxWorks: the real-time executive the most used in the industry. He is developed by the company Wind River which also acquired recently the rights of the real-time pSOS, a little bit former but also widely used kernel. - QNX: developed by the Canadian company QNX software, QNX is type UNIX's real-time system. He is in accordance with POSIX, allows to develop directly on the target and honorable platform the graphic Photon environment, close to X Window System. - ECOS: acronym standing for the Embeddable and Configurable Operating System, the eCOS was initially developed by the peer society Cygnus, today connected with the Software of Red Hat society. This system is adapted to the solutions of very low imprint memory and profoundly buried. Its environment of development is based on LINUX and chain of compilation GNU with conformity in standard (standard POSIX). 3.3 Forced by the systems owners The majority of the systems owners described this above suffer however some binding strong defects. The systems are often realized by medium-sized societies which have difficulty in following the technological evolution: the material evolves very fast, the standards software also makes more and more equipments require the integration of the constituents that we owe importer of the world of the classic computer systems or the multimedia. Therefore, the costs of license and the rights of redistribution of the systems (or royalties) are sometimes very high. The development cost of applications around systems owners is often more raised because the tools of development are badly known of the majority of developers available on the labor market. It is thus necessary to recruit of the very specialized staff. The formations around these tools are also expensive because very specialized what obliges the editor to practice costs raised to compensate for the lack of effect of mass. All this imply a set of binding specificities for the global management of the computing tools of the company. For it we have to migrate to the open source systems. 3.4 Advantages of the open source The following three points of the definition of the open source software are fundamental in the case of the embarked and real- time software: The redistribution without royalties. This point solves the economic problem of the rights of redistribution or royalties, very binding in the case of a system distributed on a large scale. The availability of the code source. This point is even more fundamental because it is on the base of the conception of a software quality and especially maintainable in the time. The possibility of realizing a development derived of this code source. The open source allows realizing substantial savings by integrating existing components into an industrial solution. 3.5 LINUX as real-time system Strong by the arguments concerning the open source, it is normal to be tried by the use of LINUX as real-time system. Besides the advantages inherent to the open source, the legendary reliability of LINUX in fact an ideal candidate. Regrettably, LINUX is not natively a real-time system. The kernel LINUX was indeed conceived with the aim of making a non-specialized system based on the notion of shared time and not real time. Computer System (system Controller) Process (Controlled system) Actuator Sensors Reactions (Stuff) Stimuli
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This article discusses over a new approach for the distributed multi - agents architectures, and the
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