Sylvain Vauttier

Improving Exception Handling in Multi-agent Systems

New software architectures based on multi-agents or software components allow the integration of separately developed software pieces that interact through various communication schemes. In such a context, reliability raises new important issues. This paper aims at increasing reliability in multi-agent systems (MASs) and, therefore, focuses on the study of an appropriate exception handling system (EHS). The issues specific to exception handling in MASs – preservation of the agent paradigm and support of cooperative concurrency – are presented and discussed. This paper analyses existing EHSs according to these issues and describes our proposition, the Sage system, which integrates various solutions from existing EHSs and adapts them to the agent paradigm. Sage is an exception handling system dedicated to MASs that addresses the stressed issues by providing means to coordinate the collective activities of agents, to embbed contextualized handlers in agents and to concert exceptions. It has been implemented and integrated in the MadKit MAS. It has been experimented with a classical travel agency case study.

WSPAB: A Tool for Automatic Classification & Selection of Web Services Using Formal Concept Analysis

The increased popularity of web services is accompanied with an increase in both provider and service number. This fairly large service number causes a deficiency in the selection of the most pertinent service, and makes it an effortful and time-consuming task.We propose the WSPAB (Web Service Personal Address Book) tool that aims at defining a complete solution for facilitating the task of finding the most pertinent web service. This includes two sub tasks, discovering and selecting. In this paper, we present the first part of the tool concerning the automation of the selection process, taking into consideration the quality of service (QoS) and user preferences. The WSPAB accomplishes the automatic selection of a service by filtering web services according to certain aspects of QoS and certain user requirements; then classifying these services using the formal concept analysis (FCA) approach, enabling users to easily select their needed service, identify its potential substitutes and keep trace of them either for future use, or to be shared with others.

Exception handling and asynchronous active objects: issues and proposal

Asynchronous Active Objects (AAOs), primarily exemplified by actors [1], nowadays exist in many forms (various kinds of actors, agents and components) and are more and more used because they fit well the dynamic and asynchronous nature of interactions in many distributed systems. They raise various new issues regarding exception handling for which few operational solutions exist. More precisely, a need exists for a generic, simple and expressive, programmer level, exception handling system that appropriately handles the following main exception handling issues or requirements in the context of AAOs: encapsulation, object autonomy, coordination of concurrent collaborative entities [2], “caller contextualization” [3], asynchronous signaling and handler execution, resolution of concurrent exceptions [4,5], exception criticality [6] and object reactivity. This paper presents the specification of an evolution of the Sage exception handling system [7], which provides solutions to those issues in the context of systems developed with active objects using one way asynchronous communications and interacting via the request / response protocol. Such a context, in which synchronizations constraints are, when needed, handled at the application level, allows for a very generic view of what could be done regarding exception handling in all systems that use active objects. The Sage solution is original and provides a good compromise between expressive-power and simplicity.

Mining features from the object-oriented source code of software variants by combining lexical and structural similarity

Migrating software product variants which are deemed similar into a product line is a challenging task with main impact in software reengineering. To exploit existing software variants to build a software product line (SPL), the first step is to mine the feature model of this SPL which involves extracting common and optional features. Thus, we propose, in this paper, a new approach to mine features from the object-oriented source code of software variants by using lexical and structural similarity. To validate our approach, we applied it on ArgoUML, Health Watcher and Mobile Media software. The results of this evaluation showed that most of the features were identified1.

Feature Location in a Collection of Software Product Variants Using Formal Concept Analysis

Formal Concept Analysis (FCA) is a theoretical framework which structures a set of objects described by properties. In order to migrate software product variants which are considered similar into a product line, it is essential to identify the common and the optional features between the software product variants. In this paper, we present an approach for feature location in a collection of software product variants based on FCA. In order to validate our approach we applied it on a case study based on ArgoUML. The results of this evaluation showed that all of the features were identified.

Using Concept Lattices to Support Web Service Compositions with Backup Services

In SOA, composite applications can be developed on the basis of collections of interacting web services. A services functionality is exposed to the external world by an abstract interface, described by the standard WSDL language, which must be published by service providers to public registries where service consumers can find them. Nowadays, web service discovery has become a real problem, because of the lack of public registries to publish and organize the fairly huge number of existing services. In this paper, we propose an approach based on formal concept analysis (FCA) for classifying and browsing web services. Using this approach, the web services are organized into a lattice structure, to facilitate their browse and selection. A service lattice reveals the invisible relations between the services, enabling the discovery of a needed service as well as the identification of its possible alternatives. Thus, service discovery may be achieved more easily using the service lattice. This facilitates the construction of service compositions and supports them with backup services to ensure a continuous functionality.

Architecture-centric component-based development needs a three-level ADL

Architecture-centric, component-based development intensively reuses components from repositories. Such development processes produce architecture definitions, using architecture description languages (Adls). This paper proposes a three step process. Architecture specifications first capture abstract and ideal architectures imagined by architects to meet requirements. Specifications do not describe complete component types but only component roles (usages). Architecture configurations then capture implementation decisions, as the architects select specific component classes from the repository to implement component roles. Finally, architecture assemblies define how components instances are created and initialized to customize the deployment of architectures in their own execution contexts. This development process is supported by a three-level Adl which enables the separate definition of these three representations. The refinement relationships between these architecture representations are also discussed.

Backing composite web services using formal concept analysis

A Web service is a software functionality accessible through the network. Web services are intended to be composed into coarser-grained applications. Achieving a required composite functionality requires the discovery of a collection of Web services out of the enormous service space. Each service must be examined to verify its provided functionality, making the selection task neither efficient nor practical. Moreover, when a service in a composition becomes unavailable, the whole composition may become functionally broken. Therefore, an equivalent service must be retrieved to replace the broken one, thus spending more time and effort. In this paper, we propose an approach for Web service classification based on FCA, using their operations estimated similarities. The generated lattices make the identification of candidate substitutes to a given service straightforward. Thus, service compositions can be achieved more easily and with backup services, so as to easily recover the functionality of a broken service.

Formal Concept Analysis-Based Service Classification to Dynamically Build Efficient Software Component Directories

Component directories index components by the services they offer thus enabling us to rapidly access them. Component directories are also the cornerstone of dynamic component assembly evolution when components fail or when new functionalities have to be added to meet new requirements. This work targets semi-automatic evolution processes. It states the theoretical basis of on-the-fly construction of component directories using formal concept analysis based on the syntactic description of the services that components require or provide. In these directories, components are more clearly organised and new abstract and highly reusable component external descriptions suggested. Moreover, this organisation speeds up both automatic component assembly and automatic component substitution.

Automated and unanticipated flexible component substitution

In this paper, we present an automatic and flexible approach for software component substitution. When a component is removed from an assembly, most existing approaches perform component-to-component substitution, relying on the fact that such a candidate component is available, which is hardly to happen because the constraints on its interfaces are too strong. When such a component does not exist, it would be more flexible to allow a single component to be replaced by a whole component assembly. We propose such an automatic substitution mechanism which does not need the changes to be anticipated and preserves the quality of the assembly.