Salima Benbernou

On the Evolution of Services

In an environment of constant change and variation driven by competition and innovation, a software service can rarely remain stable. Being able to manage and control the evolution of services is therefore an important goal for the Service-Oriented paradigm. This work extends existing and widely adopted theories from software engineering, programming languages, service-oriented computing, and other related fields to provide the fundamental ingredients required to guarantee that spurious results and inconsistencies that may occur due to uncontrolled service changes are avoided. The paper provides a unifying theoretical framework for controlling the evolution of services that deals with structural, behavioral, and QoS level-induced service changes in a type-safe manner, ensuring correct versioning transitions so that previous clients can use a versioned service in a consistent manner.

Semantic retrieval of multimedia data

This paper deals with the problem of finding multimedia data that fulfill the requirements of user queries. We assume both the user query and the multimedia data are expressed by MPEG-7 standard. The MPEG-7 formalism lacks the semantics and reasoning support in many ways. For example, the search of the implicit data can not be achieved, due to its description based on XML schema. We propose a framework for querying multimedia data based on a tree embedding approximation algorithm, combining the MPEG-7 standard and an ontology.

Evolving Services from a Contractual Perspective

In an environment of constant change, driven by competition and innovation, a service can rarely remain stable - especially when it depends on other services to fulfill its functionality. However, uncontrolled changes can easily break the existing relationships between a service and its environment (its customers and providers). In this paper we present an approach that allows for the controlled evolution of a service by leveraging the loosely-coupled nature of the SOA paradigm. More specifically, we formalize the notion of contracts between interacting services that enable their independent evolution and we investigate under which criteria can changes to a contract-bound service, or even to the contract itself, be transparent to the environment of the service.

Adaptation of service-based systems

The advances in modern technology development and future technology changes dictate new challenges and requirements to the engineering and provision of services and service-based systems (SBS). These services and systems should become drastically more flexible; they should be able to operate and evolve in highly dynamic environments and to adequately react to various changes in these environments. In these settings, adaptability becomes a key feature of services as it provides a way for an application to continuously change itself in order to satisfy new contextual requirements.

Privacy-Aware Web Service Protocol Replaceability

Business protocols are becoming a necessary part of Web services description [4]. The work presented in [4] investigates mechanisms for analyzing the compatibility and the substitution (i.e., replaceability) of Web services based on their functional properties. In this paper, we focus on the replaceability analysis. Whether a service can replace another depends not only on their functional properties but also on non functional requirements (e.g., privacy policies). We propose a privacy-aware protocol replaceability approach to extend the work presented in [4] by privacy properties. We introduce a rule-based privacy model and we extend business protocols, leading to what we call private business protocols. Finally, a private replaceability analysis of private business protocols is discussed. We mainly investigate compatibility issues, that is whether one private business protocol can support the same set of conversations with respect to the privacy requirements.

A Soft Constraint-Based Approach to QoS-Aware Service Selection

Service-based systems should be able to dynamically seek replacements for faulty or underperforming services, thus performing self-healing. It may however be the case that available services do not match all requirements, leading the system to grind to a halt. In similar situations it would be better to choose alternative candidates which, while not fulfilling all the constraints, allow the system to proceed. Soft constraints, instead of the traditional crisp constraints, can help naturally model and solve replacement problems of this sort. In this work we apply soft constraints to model SLAs and to decide how to rebuild compositions which may not satisfy all the requirements, in order not to completely stop running systems.

Run-Time Monitoring for Privacy-Agreement Compliance

This paper addresses the problem of monitoring the compliance of privacy agreement that spells out a consumers privacy rights and how consumer private information must be handled by the service provider. A state machine based model is proposed to describe the Private Data Use Flow (PDUF) toward monitoring which can be used by privacy analyst to observe the flow and capture privacy vulnerabilities that may lead to non-compliance. The model is built on top of (i) properties and timed-related privacy requirements to be monitored that are specified using LTL (Linear Temporal logic) (ii) a set of identified privacy misuses.

Resolution and constraint propagation for semantic Web services discovery

The purpose of semantic web services discovery is to use semantic knowledge to find services that can be composed to form an admissible answer to a query. In this paper we consider the advantage of adopting a knowledge-based approach to web services discovery. Services are described by means of terminological axioms and constrained clauses. We apply a specific resolution and a constraint propagation mechanism to evaluate queries over services.

Analytical quality assurance

As we described in Chapter 1, Services are often provisioned within short-term, volatile and highly dynamic (business) processes. These processes are designed in an abstract manner and when instantiated can involve service providers not known of during the design time of the service-based application. Thus, different from traditional software systems, service-based applications require the composition and coordination of services within highly distributed environments, cutting across the administrative boundaries of various organizations.

A logic based approach for the multimedia data representation and retrieval

Nowadays, the amount of multimedia data is increasing rapidly, and hence, there is an increasing need for efficient methods to manage the multimedia content. This paper proposes a framework for the description and retrieval of multimedia data. The data are represented at both the syntactic (structure, metadata and low level features) and semantic (the meaning of the data) levels. We use the MPEG-7 standard, which provides a set of tools to describe multimedia content from different viewpoints, to represent the syntactic level. However, due to its XML schema based representation, MPEG-7 is not suitable to represent the semantic aspect of the data in a formal and concise way. Moreover, inferential mechanisms are not provided. To alleviate these limitations, we propose to extend MPEG-7 with a domain ontology, formalized using a logical formalism. Then, the semantic aspect of the data is described using the ontologys vocabulary, as a set of logical expressions. We enhance the ontology by a rules layer, to describe more complex constraints between domain concepts and relations. Users queries may concern the syntactic and/or semantic features. The syntactic constraints are expressed using XQuery language and evaluated using an XML query engine; whereas the semantic query constraints are expressed using a rules language and evaluated using a specific resolution mechanism.