Browsing by Author "Ahmed-Nacer, Mohamed"

Now showing 1 - 16 of 16
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    A formal model for output multimodal HCI
    (Springer Vienna, 2015-07) Mohand Oussaïd, Linda; Ait Sadoune, Idir; Ait Ameur, Yamine; Ahmed-Nacer, Mohamed
    Multimodal human–computer interaction (HCI) combine modalities at an abstract specification level in order to get information from the user (input multimodality) and to return information to the user (output multimodality). These multimodal interfaces use two mechanisms: first, the fusion of information transmitted by the user on different modalities during input interaction and second, the fission or decomposition of information produced by the functional core in order to distribute the composite information on the different modalities during output interaction. In this paper, we present a generic approach to design output multimodal interfaces. This approach is based on a formal model, composed of two models: semantic fission model for information decomposition process and allocation model for modalities and media allocation to composite information. An Event-B formalization has been proposed for the fission model and for allocation model. This Event-B formalization extends the generic model and support the verification of some relevant properties such as safety or liveness. An example of collision freeness property verification is presented in this paper.
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    A generic formal model for fission of modalities in output multi-modal interactive systems
    (2009) Mohand Oussaïd, Linda; Ait Ameur, Yamine; Ahmed-Nacer, Mohamed
    Output multi-modal human-machine interfaces combine semantically output medias and modalities in order to increase interaction machine capabilities. The aim of this paper is to present a formal model supporting formal specifications of output multi-modal interactive systems. As a consequence, the expected usability and robustness properties can be expressed and checked. This paper proposes a generic model which permits to specify the output multimodal interfaces following the CASE design space.
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    A MOF-based Social Web Services Description Metamodel
    (CERIST, 2015-12-09) Benna, Amel; Maamar, Zakaria; Ahmed-Nacer, Mohamed
    To make IT community adopt social Web services, both social Web service-based applications and their support platforms should evolve independently from each other while sharing a common model that represent the characteristics of these social Web services. This paper proposes a model-driven approach that achieves this duality. First, the approach identifies a social Web service's properties. Then a Meta-Object-Facility(MOF)-based social Web services description metamodel is developed. A prototype illustrates how the proposed MOF-based metamodel is used.
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    Cerist News
    (2012-12) CERIST; Ahmed-Nacer, Mohamed
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    Game theory for Initial Public Offering (IPO): A multi-agent approach
    (CERIST, 2012) Hedjazi Dellal, Badiâa; Ahmed-Nacer, Mohamed; Aknine, Samir; Benatchba, Karima
    This work consists in simulating a real time interbank gross payment system (RTGS) through a multi-agent model, to analyze the evolution of the liquidity brought by the banks to the system. In this model, each bank chooses the amount of a daily liquidity on the basis of costs minimization (costs of liquidity and delaying) by taking into account the liquidity brought by the other banks. Banks agents’ strategies are based on a liquidity game during several payment days where each bank plays against the others. For their adaptability, we integrate into bank agents learning classifier systems. We carry out several simulations to follow the system total liquidity evolution as that of each bank agent with varying costs coefficients. The question to answer is: what are the cash amounts that banks must provide and under what costs of liquidity and delaying, the system avoids the lack of liquidity? We find that liquidity depends on costs coefficients.
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    Interbank payment system (RTGS) simulation using multi-agent approach
    (CERIST, 2011-10) Hedjazi Dellal, Badiâa; Ahmed-Nacer, Mohamed; Aknine, Samir
    This work consists in simulating a real time interbank gross payment system (RTGS) through a multi-agent model, to analyze the evolution of the liquidity brought by the banks to the system. In this model, each bank chooses the amount of a daily liquidity on the basis of costs minimization (costs of liquidity and delaying) by taking into account the liquidity brought by the other banks. Banks agents’ strategies are based on a liquidity game during several payment days where each bank plays against the others. For their adaptability, we integrate into bank agents learning classifier systems. We carry out several simulations to follow the system total liquidity evolution as that of each bank agent with varying costs coefficients. The question to answer is: what are the cash amounts that banks must provide and under what costs of liquidity and delaying, the system avoids the lack of liquidity? We find that liquidity depends on costs coefficients.
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    Un modèle de composition des services web sémantiques
    (CERIST, 2008-09) Temglit, Nacéra; Aliane, Hassina; Ahmed-Nacer, Mohamed
    Le travail présenté ici vise à proposer un modèle pour la composition des services web sémantiques. Ce modèle est basé sur une représentation sémantique de l'ensemble des concepts manipulés par les services web d’un domaine d'application, à savoir, les opérations et les concepts statiques utilisés pour décrire les propriétés des services web. Différents niveaux d'abstraction sont donnés au concept opération pour permettre un accès progressif aux services concrets. Ainsi, deux plans de composition à granularités différentes (abstrait et concrets) sont générés. Ceci permettra de réutiliser des plans déjà construits pour répondre à des besoins similaires et même avec des préférences modifiées.
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    modélisation formelle d'IHM multi-modales en sortie avec B Evénementiel
    (CERIST, 23-04-2014) Mohand Oussaïd, Linda; Ait Sadoune, Idir; Ait Ameur, Yamine; Ahmed-Nacer, Mohamed
    Les interfaces homme-machine (IHM) multi-modales offrent à l’utilisateur la possibilité de combiner les modalités d’interaction afin d’augmenter la robustesse et l’utilisabilité de l’interface utilisateur d’un système. Plus particulièrement, en sortie, les IHM multi-modales permettent au système de restituer à l’utilisateur, l’information produite par le noyau fonctionnel en combinant sémantiquement plusieurs modalités. Dans l’optique de concevoir de telles interfaces pour des systèmes critiques, nous avons proposé un modèle formel de conception des interfaces multi-modales en sortie. Le modèle proposé se décompose en deux modèles : le modèle de fission sémantique qui décrit la décomposition de l’information à restituer en informations élémentaires, et le modèle d’allocation qui spécifie l’allocation des modalités et médias aux informations élémentaires. Nous avons également développé une formalisation B Événementiel détaillée des deux modèles : fission sémantique et allocation. Cet article est dédié à la présentation d’une démarche formelle et générique relative au modèle proposé, il décrit la démarche générale de développement B Événementiel ainsi que le modèle générique B Événementiel correspondant au modèle de conception générique.
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    Multi-Agent Liquidity Risk Management in an Interbank Net Settlement System
    (Springer Berlin Heidelberg, 2012) Hedjazi Dellal, Badiâa; Ahmed-Nacer, Mohamed; Aknine, Samir; Benatchba, Karima
    A net settlement system is a payment system between banks, where a large number of transactions are accumulated, usually waiting until the end of each day to be settled through payment instruments like: wire transfers, direct debits, cheques, .... These systems also provide clearing functions to reduce interbank payments but are sometimes exposed to liquidity risks. Monitoring, and optimizing the interbank exchanges through suitable tools is useful for the proper functioning of these systems. The goal is to add to these systems an intelligent software layer integrated with the existing system for the improvement of transactions processing and consequently avoid deadlock situations, deficiencies and improve system efficiency. We model and develop by multi-agent an intelligent tracking system of the interbank exchanged transactions to optimize payments settlement and minimize liquidity risks.
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    Multi-agent liquidity risk management in an interbank net settlement system
    (CERIST, 2012-09) Hedjazi Dellal, Badiâa; Ahmed-Nacer, Mohamed; Aknine, Samir; Benatchba, Karima
    A net settlement system is a payment system between banks, where a large number of transactions between the banks are accumulated, usually waiting until the end of each day to be settled trough payment instruments like: wire transfers, direct debits, cheques, bank cards... These systems also provide clearing functions to reduce the number of interbank payments to achieve but are sometimes exposed to liquidity risks. Monitoring, controlling and optimizing the interbank exchanges through suitable tools is useful for the proper functioning of these systems. The goal is to add to these systems an intelligent software layer integrated with the existing system for the improvement and multilateral optimization of transactions and consequently avoid deadlock situations, bypass certain deficiencies and improve system efficiency. We model and develop by multi-agent an intelligent tracking system of the exchanged transactions through an interbank clearing system, to optimize payments settlement and minimize liquidity risks.
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    OVERHEARING IN FINANCIAL MARKETS: A Multi-agent Approach
    (SciTePress Science and Technology Publications, 2011) Hedjazi Dellal, Badiâa; Aknine, Samir; Ahmed-Nacer, Mohamed; Benatchba, Karima
    Open complex systems as financial markets evolve in a highly dynamic and uncertain environment. They are often subject to significant fluctuations due to unanticipated behaviours and information. Modelling and simulating these systems by means of agent systems, i.e., through artificial markets is a valuable approach. In this article, we present our model of asynchronous artificial market consisting of a set of adaptive and heterogeneous agents in interaction. These agents represent the various market participants (investors and institutions). Investor Agents have advanced mental models for ordinary investors which do not relay on fundamental or technical analysis methods. On one hand, these models are based on the risk tolerance and on the other hand on the information gathered by the agents. This information results from overhearing influential investors in the market or the order books. We model the system through investor agents using learning classifier systems as reasoning models. As a result, our artificial market allows the study of overhearing impacts on the market. We also present the experimental evaluation results of our model.
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    Overhearing in financial markets: a multi-agent approach markets: a multi-agent approach
    (CERIST, 2010-11) Hedjazi Dellal, Badiâa; Ahmed-Nacer, Mohamed; Aknine, Samir; Benatchba, Karima
    Open complex systems as financial markets evolve in a highly dynamic and uncertain environment. They are often subject to significant fluctuations due to unanticipated behaviours and information. Modelling and simulating these systems by means of agent systems, i.e., through artificial markets is a valuable approach. In this article, we present our model of asynchronous artificial market consisting of a set of adaptive and heterogeneous agents in interaction. These agents represent the various market participants (investors and institutions). Investor Agents have advanced mental models for ordinary investors which do not relay on fundamental or technical analysis methods. On one hand, these models are based on the risk tolerance and on the other hand on the information gathered by the agents. This information results from overhearing influential investors in the market or the order books. We model the system through investor agents using learning classifier systems as reasoning models. As a result, our artificial market allows the study of overhearing impacts on the market. We also present the experimental evaluation results of our model.
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    Semantic web service composition: Multi-level based approach
    (CERIST, 2009-03) Temglit, Nacéra; Ahmed-Nacer, Mohamed
    Web service composition has quickly become a key area of research in the services oriented architecture community. It is originated from the necessity to combine existing services to achieve a predetermined goal that cannot be realized by a standalone service. Semantic service description is supposed to be the key element for dynamic composition of Web services, since it enables rich machine understandable descriptions of their capabilities and parameters [7]. This paper introduces a framework for performing dynamic service composition based on three level of semantic description and organization of web services. Thus, we present three main phases to generate composite service from high-level declarative Query. Two level granularities of composition plan are gradually generated (abstract and concrete) using our approach. This will reuse plans already constructed to meet similar needs even with modified preferences. The core of our proposed composition process is the matchmaking algorithm extended from that of [13].
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    Towards an intrusion detection system : a critical and comparative study
    (CERIST, 2008) Bensefia, Hassina; Ahmed-Nacer, Mohamed
    An Intrusion Detection System(IDS), that is destined to supervise an environment, must adjust itself according to every change in the environment and be handling every new attack occurrence. This feature is referred to as the adaptability. It makes the IDS a learning system in relation to its target environment, practicing an autonomous and continuous learning of new attacks. This paper develops a critical and comparative study of existing adaptive intrusion detection models. The objective of such study is to be oriented with regard to related works in the aim of building our own vision to add contribution in the IDS adaptability context.
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    Using MDA approach to enhance Web services description with social information
    (CERIST, 2013-05) Benna, Amel; Ahmed-Nacer, Mohamed
    Recent research on Web services has demonstrated the need of including the social dimension into different stages of the Web service lifecycle. Also researchers have found that social relationships between Web services can be identified using social network concepts. However, much of these works are focused on how to discover/recommend, secure, build and manage social networks but do not describe how to develop a social Web service and what would be its description. Our goal in this paper is to enhance Web services description with social information using the MDA approach. We first propose a social Web services interaction metamodel to be used as a basis for the development of social Web services application and an association platform. The social Web services interaction metamodel concepts are grouped according to different views. Each of these views is represented by a Metamodel based Meta Object Facility (MOF) package. The social services metamodel is then transformed to social Web services description schema that validates standards Web services description. Finally, a sample application of the social Web services description model and its associated schema has been implemented based on the instantiation of the proposed metamodel.
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    Vérification formelle des propriétés de sécurité des logiciels
    (Institut National de Formation en Informatique (INI), 2006) Mohand Oussaïd, Linda; Ahmed-Nacer, Mohamed
    Cette thèse présente une démarche de vérification formelle des propriétés de sécurité des logiciels. En effet, après étude des approches possibles : preuve formelle et model checking, nous avons identifié le model checking comme étant l'approche la plus adéquate pour notre problématique. Ainsi, la démarche proposée est fondée sur une combinaison de la technique de model checking et des mécanismes : d'annotation et d'abstraction basés sur l'interprétation abstraite. Pour procéder au model checking, nous avons commencé par exprimer les propriétés de sécurité (confidentialité, intégrité, disponibilité) dans une logique temporelle appropriée. Ensuite, nous avons spécifié les systèmes auxquels pouvait s'appliquer notre démarche à savoir : les systèmes dont l'évolution peut être assimilée à un programme impératif réduit aux structures de contrôle de base. Moyennant deux étapes : la première qui enrichit le code source par des informations relatives à la propriété à vérifier et la deuxième qui débarrasse le code source enrichi des informations superflues à la vérification de la propriété de sécurité, nous avons transformé le code source d'un programme impératif en un programme abstrait qui exhibe les instructions concernées par les propriétés à vérifier tout en faisant abstraction du reste. L'annotation aussi bien que l'abstraction ont été développées par interprétation abstraite autour d'une correspondance de Galois qui assure que le programme abstrait correspond au programme initial. Cette démarche a été illustrée par un exemple qui consiste en un gestionnaire de transactions bancaires simplifié.