Mohamed Jmaiel

Electing a leader in the local computation model using mobile agents

Needless to say, distributed algorithms are usually hard to design mush harder to prove and to use in real distributed systems. In these systems, local computations theory has proved its power to formalize and prove in an intuitive way distributed algorithms. This paper uses this formalism to present solutions to the election problem in several network topologies using mobile agents at the design and the implementation levels. We formalized the proposed solutions in the local computations model using transition systems [11]. This facilitates the proof of the proposed solutions using the mathematical tool-box provided by the local computation theory. Using mobile agents, the proposed solutions get rid of synchronization and do not need continuous use of all machines computational resources. Proposed solutions are also simulated within the VISIDIA [3] platform.

Specification and verification of multi-agent applications using temporal Z

This work suggests a formal approach for specifying and verifying multi-agent applications. This approach provides a specification language which integrates temporal logic in the Z notation allowing, in this way, to cover static, behavioural, as well as dynamic aspects of a multi-agent application. Then, we present the syntax and the semantics of the proposed language, particularly, we provide a temporal model according to the framework of Z. Our approach allows us to rigourously reason about interesting properties of multi-agent systems. Finally, we illustrate our approach by verifying an agent based specification for the pursuit problem. We make use of the Z/EVES tools to analyse and reason about our specifications.

A QoS-Driven Reconfiguration Management System Extending Web Services with Self-Healing Properties

This paper addresses QoS management for self-healing Web services. The objective is to provide a healing framework based on service monitoring and architectural-level repair actions. We address these topics in the context of the European project WS-DIAMOND. We implemented and assessed a connector-based healing layer capable of intercepting, analyzing and enhancing SOAP traffic and message contents with QoS data. Our framework supports Service Monitoring and dynamic run-time reconfiguration based on reflective programming.

A Comprehensive Ontology-Based Approach for SLA Obligations Monitoring

Specifying clear quality of service (QoS) agreements between service providers and consumers is particularly important for the successful deployment of service-oriented architectures. The related challenges include correctly elaborating and monitoring QoS contracts (SLA: service level agreement) to detect and handle their violations. In this paper, first, we study and analyze existing SLA-related models. Then, we elaborate a complete, generic and semantically richer ontology-based model of SLA. We used the Semantic Web Rule Language (SWRL) to express SLA obligations in our model. This language facilitates the SLA monitoring process and the eventual action triggering in case of violations. We used this model to automatically generate semantic-enabled QoS obligations monitors. We have also developed a prototype to validate our model and our monitoring approach. Finally, we believe that this work is a step ahead to the total automation of the SLA management process.

Specification and design of multi-agent applications using temporal z

This paper proposes a formal approach, based on stepwise refinements, for specifying and designing multi-agent applications. This approach provides a specification language which integrates temporal logic in the Z notation allowing, in this way, to cover static, behavioural, as well as dynamic aspects of multi-agent systems. Moreover, it proposes a methodology giving a set of hints and principles which help and guide the design process. Indeed, this methodology enables the user to develop step by step, in an incremental way, an implementation starting from an abstract requirements (goal) specification. Finally, we illustrate our approach by developing an agent based solution for the pursuit problem.

D-CEP4CMA: a dynamic architecture for cloud performance monitoring and analysis via complex event processing

This paper presents a dynamic monitoring and analysis architecture for Cloud computing environments. It collects and analyses Cloud parameters to detect performance degradations. The proposed dynamic architecture, called D-CEP4CMA, is based on the methodology of complex event processing (CEP). It is designed to dynamically switch between different centralised and distributed CEP architectures depending on the load/memory of the CEP machine and network traffic conditions in the observed cloud environment. Experimental results demonstrate the efficiency of D-CEP4CMA and its performance in terms of precision and recall in comparison to centralised and distributed CEP architectures.

A Distributed Computational Model for Mobile Agents

In this paper, a novel formalized mobile agent distributed computation model based on transition systems is presented. In our model, the mobile agent actions (e.g. computations, communication and migration) are described using transitions. Thus, a mobile agent algorithm is viewed as a transition system and the underlying distributed system is modeled by a connected graph. We exploit the high-level encoding of agent actions by transitions to prove the correctness of agent algorithms. We illustrate this approach with the distributed computation of a spanning tree.

Towards a formal methodology for designing multi-agent applications

This paper has two purposes. First, it defines a formal language for specifying multi-agent systems. This language is expressive enough to cover individual agent aspects (knowledge, goals, roles, ...) as well as collective aspects of in terms of coordination protocols, organization structure and planning activities. Second, it provides a formal design methodology based on stepwise refinements allowing to develop a design specification starting from an abstract requirements one.

Enhancing Client Intentions Analysis for Service Level Agreements Establishment Assistance

Service Level Agreements (SLAs) are a mean to guarantee quality of service terms between providers and consumers. Obviously, it is very important to ensure a clear and fair establishment of these SLAs. This issue has not been well addressed, especially when providers and clients do not share the same knowledge degree. In many cases, clients have to select a subset of predefined technical choices by the providers. However, non expert clients may not understand these choices. To address this problem, we started by modeling client intentions and provider offers using ontologies. This helped us to develop an automatic matching approach between these models in order to bridge the gap between the client and the provider knowledge. Our matching approach is composed of three steps. The first step consists in generating correspondences between the client and the provider terms by assigning certainties for their equivalence. The second step corrects and refines these certainties. In the third step, we evaluate the matching results using inference rules to facilitate the automatic generation of a Service Level Agreement draft.

LMF-QL: A Graphical Tool to Query LMF Databases for NLP and Editorial Use

LMF is an new standard (ISO 24613) whose objective is to unify the representation of lexical resources in an XML database. LMF databases have generally complex structures which make formulating queries for extracting lexical data a hard task. Indeed, formulating a query necessitates mastering both the document structure and a query language. So in order to assist the query formulation for unskilled users and speed up this task for professional ones, we present in this paper a powerful and user-friendly graphical tool enabling automatic generation of XQuery queries for extracting lexical data from LMF databases for NLP and editorial use. To this end, we abstract database structure for specification of a query for data extraction. So, this tool accepts the query specification in term of Input and Output, where user may select only some data categories.