Djamal Benslimane

Services Mashups: The New Generation of Web Applications

Web services are becoming a major technology for deploying automated interactions between distributed and heterogeneous applications, and for connecting business processes. Service mashups indicate a way to create new Web applications by combining existing Web resources utilizing data and Web APIs. They facilitate the design and development of novel and modern Web applications based on easy-to-accomplish end-user service compositions.

What can context do for web services

Context-aware Web service would significantly benefit the interactions between human, applications, and the environment.

A context-based mediation approach to compose semantic Web services

Web services composition is a keystone in the development of interoperable systems. However, despite the widespread adoption of Web services, several obstacles still hinder their smooth automatic semantic reconciliation when being composed. Consistent understanding of data exchanged between composed Web services is hampered by various implicit modeling assumptions and representations. Our contribution in this article revolves around context and how it enriches data exchange between Web services. In particular, a context-based mediation approach to solve semantic heterogeneities between composed Web services is presented.

Towards an Approach forWeb services Substitution

This paper presents an approach whose objective is to support Web services substitution. Substitution means replacing a component with another component, as long as the replacing component produces the same output and satisfies the same requirements as the replaced component. Motives for substitution include Web services non-responsiveness to client requests and better arrangement with another, competitor Web service. To perform Web services substitution with less impact on the ongoing, and sometimes critical, business processes, the approach proposes deploying communities of Web services. A community promotes the dynamic binding of Web services through a common interface, known as open service connectivity. The open service connectivity directs requests to and responses from Web services regardless of how these latter are specified, implemented, and located

An Argumentation Framework for Communities of Web Services

As the number of Web services continues to increase, so does the opportunities to compose them to build more complex and complete business solutions. To facilitate and speed up Web-services discovery, Web services with similar (or equivalent) functionalities - such as flight booking and travel reservation - can be grouped into communities. Argumentation theory, implemented through a set of software agents that reason about Web services, can improve Web services performance through the notion of communities.

An Approach to Engineer Communities of Web Services: Concepts, architecture, operation, and deployment

This article presents an approach that provides the necessary assistance to those who are in charge of engineering communities of Web services. Current practices indicate that Web services providing the same functionality are gathered into one community, independently of their origins and the way they carry out this functionality. The provided assistance manifests itself with the concepts to use, the architecture to select, the operations to script, and the deployment to track. Two protocols frame the interactions in an environment of communities of Web services namely the Web Services Community Development Protocol and the Contract-Net Protocol. The former manages a community in terms of Web services attraction/registration/withdrawal to/with/from this community. The latter satisfies users’ needs in terms of Web services selection/contracting/triggering. Finally, the article presents a prototype illustrating the engineering approach with focus on Web services attraction.

Wrapper-based evolution of legacy information systems

System evolution most often implies the integration of legacy components, such as databases, with newly developed ones, leading to mixed architectures that suffer from severe heterogeneity problems. For instance, incorporating a new program in a legacy database application can create an integrity mismatch, since the database model and the program data view can be quite different (e.g. standard file model versus OO model). In addition, neither the legacy DBMS (too weak to address integrity issues correctly) nor the new program (that relies on data server responsibility) correctly cope with data integrity management. The component that can reconciliate these mismatched subsystems is the R/W wrapper, which allows any client program to read, but also to update the legacy data, while controlling the integrity constraints that are ignored by the legacy DBMS.This article describes a generic, technology-independent, R/W wrapper architecture, a methodology for specifying them in a disciplined way, and a CASE tool for generating most of the corresponding code.The key concept is that of implicit construct, which is a structure or a constraint that has not been declared in the database, but which is controlled by the legacy application code. The implicit constructs are elicited through reverse engineering techniques, and then translated into validation code in the wrapper. For instance, a wrapper can be generated for a collection of COBOL files in order to allow external programs to access them through a relational, object-oriented or XML interface, while offering referential integrity control. The methodology is based on a transformational approach that provides a formal way to build the wrapper schema and to specify inter-schema mappings.

On the Use of Fuzzy Dominance for Computing Service Skyline Based on QoS

Nowadays, the exploding number of functionally similar Web services has led to a new challenge of selecting the most relevant services using quality of service (QoS) aspects. Traditionally, the relevance of a service is determined by computing an overall score that aggregates individual QoS values. Users are required to assign weights to QoS attributes. This is a rather demanding task and an imprecise specification of the weights could result in missing some user desired services. Recent approaches focus on computing service skyline over a set of QoS aspects. This can completely free users from assigning weights to QoS attributes. However, two main drawbacks characterize such approaches. First, the service skyline often privileges services with a bad compromise between different QoS attributes. Second, as the size of the service skyline may be quite large, users will be overwhelmed during the service selection process. In this paper, we introduce a new concept, called alpha-dominant service skyline, to address the above issues and we develop a suitable algorithm for computing it efficiently. Experimental evaluation conducted on synthetically generated datasets, demonstrates both the effectiveness of the introduced concept and the efficiency of the proposed algorithm.

Agent-based communities of web services: an argumentation-driven approach

The objective of this paper is to discuss how to sustain the growth of Web services through the use of communities. A community aims at gathering Web services with the same functionality independently of their origins, locations, and functioning. To make Web services more responsive to the environment in which they run and to be more flexible when managing communities, Web services are associated with software agents enhanced with argumentation capacities. This type of agents persuade and negotiate with other peers for the sake of letting their respective Web services reach their goals in an efficient way. Associating Web services with this type of agents allows them to select good communities and allow the communities to host the good Web services and to select the best ones for composite scenarios. Furthermore, this provides satisfactory solutions for three open problems: starvation (Web services refuse all the possibilities of joining communities), competition-free (Web services accept joining any community without being selective), and unfairness (always the same Web services members of a community are selected out of many others to participate in composite scenarios). In addition, the paper presents a formal and computational persuasive and negotiation protocol to manage the attraction and retainment of Web services in the communities and their identification for composite services.

Contextual ontologies: motivations, challenges, and solutions

Contextual ontologies are ontologies that characterize a concept by a set of properties that vary according to context. Contextual ontologies are now crucial for users who intend to exchange information in a domain. Existing ontology languages are not capable of defining such type of ontologies. The objective of this paper is to formally define a contextual ontology language to support the development of contextual ontologies. In this paper, we use description logics as an ontology language and then we extend it by introducing a new contextual constructor.