Real-time systems refinement : application to the verification of web services

Les services Web sont des applications distribuées qui sont conçus pour atteindre une tâche spécifique de l'entreprise sur le web. Afin d'augmenter la qualité et d'élever la sécurité des services Web, la vérification de BPEL, un service web langage de composition est considérée. Dans ce contexte, le model checking est une des techniques de vérification les plus utilisés en raison de son exhaustivité, son application facile et automatique. Cependant, un inconvénient majeur du model checking est l'explosion combinatoire en cas de grands modèles. Le raffinement est une des techniques utilisées pour combattre au problème d'explosion. Dans cette thèse, nous étudions le raffinement des systèmes temporisés et son application à des situations réelles, à savoir les modèles BPEL. Pour cela, nous proposons d'abord une technique automatique pour la vérification de la simulation faible temporisée entre des systèmes de transitions temporisé basée sur des modèles issus d'un langage de spécification formelle, FIACRE. La technique est une méthode basée sur l'observation, dans laquelle deux systèmes de transitions temporisés sont composées avec un observateur temporisé. Une propriété de mu-calcul qui capte la simulation faible temporisée est ensuite vérifiée sur le résultat de la composition. En deuxième étape, afin de valider les modèles BPEL, nous proposons une technique qui consiste dans les étapes suivantes: premièrement, les activités BPEL qui ont besoin d'être abstrait sont fournis avec leurs abstractions. Deuxièmement, la source BPEL est transformé en FIACRE en fonction des choix précédents. Troisièmement, les propriétés d'exigences sont vérifiées sur le modèle de FIACRE abstrait. Enfin, les relations de simulation sont prouvés entre les composants concrets et abstraits du modèle.Web services are distributed applications which are designed to achieve a specific business task over the web. In order to increase the security and to elevate the safety of web services, the verification of BPEL, a web services composition language is considered. In this context, model checking is one of the most used verification techniques because of its thoroughness, its easy application, and automatic approach. However, a major drawback of model checking is the combinatory explosion in case of large models. Refinement is one of the used techniques to alleviate the model checking problem. In this PhD, we study the refinement of timed systems and its application to real life scenarios, namely to BPEL models. For this, we first suggest an automatic technique for checking the timed weak simulation between timed transition systems based on models originating from a formal specification language, FIACRE. The technique is an observation-based method in which two timed transition systems are composed with a timed observer. A $\mu$-calculus property that captures the timed weak simulation is then verified upon the result of the composition. At the second stage, in order to validate BPEL models, we suggest a technique that consists in the following steps : first, BPEL activities to-be-abstracted are provided along with their abstractions. Second, the BPEL source is transformed to FIACRE according to the previous choices. Third, domain properties are verified on the abstract FIACRE model. Finally, simulation relations are proven between concrete and abstract parts of the model

Web Services: A Process Algebra Approach

It is now well-admitted that formal methods are helpful for many issues raised in the Web service area. In this paper we present a framework for the design and verification of WSs using process algebras and their tools. We define a two-way mapping between abstract specifications written using these calculi and executable Web services written in BPEL4WS. Several choices are available: design and correct errors in BPEL4WS, using process algebra verification tools, or design and correct in process algebra and automatically obtaining the corresponding BPEL4WS code. The approaches can be combined. Process algebra are not useful only for temporal logic verification: we remark the use of simulation/bisimulation both for verification and for the hierarchical refinement design method. It is worth noting that our approach allows the use of any process algebra depending on the needs of the user at different levels (expressiveness, existence of reasoning tools, user expertise)

On interoperability and conformance assessment in service composition

The process of composing a service from other services typically involves multiple models. These models may represent the service from distinct perspectives, e.g., to model the different roles of systems involved in the service, and at distinct abstraction levels, e.g., to model the service’s capability, interface or the orchestration that implements the service. The consistency among these models needs to be maintained in order to guarantee the correctness of the composition process. Two types of consistency relations are distinguished: interoperability, which concerns the ability of different roles to interoperate, and conformance, which concerns the correct implementation of an abstract model by a more concrete model. This paper discusses the need for and use of techniques to assess interoperability and conformance in a service composition process. The paper shows how these consistency relations can be described and analysed using concepts from the COSMO framework. Examples are presented to illustrate how interoperability and conformance can be assessed

Transitioning Applications to Semantic Web Services: An Automated Formal Approach

Semantic Web Services have been recognized as a promising technology that exhibits huge commercial potential, and attract significant attention from both industry and the research community. Despite expectations being high, the industrial take-up of Semantic Web Service technologies has been slower than expected. One of the main reasons is that many systems have been developed without considering the potential of the web in integrating services and sharing resources. Without a systematic methodology and proper tool support, the migration from legacy systems to Semantic Web Service-based systems can be a very tedious and expensive process, which carries a definite risk of failure. There is an urgent need to provide strategies which allow the migration of legacy systems to Semantic Web Services platforms, and also tools to support such a strategy. In this paper we propose a methodology for transitioning these applications to Semantic Web Services by taking the advantage of rigorous mathematical methods. Our methodology allows users to migrate their applications to Semantic Web Services platform automatically or semi-automatically

Behavioral types in programming languages

A recent trend in programming language research is to use behav- ioral type theory to ensure various correctness properties of large- scale, communication-intensive systems. Behavioral types encompass concepts such as interfaces, communication protocols, contracts, and choreography. The successful application of behavioral types requires a solid understanding of several practical aspects, from their represen- tation in a concrete programming language, to their integration with other programming constructs such as methods and functions, to de- sign and monitoring methodologies that take behaviors into account. This survey provides an overview of the state of the art of these aspects, which we summarize as the pragmatics of behavioral types

Multilevel Contracts for Trusted Components

This article contributes to the design and the verification of trusted components and services. The contracts are declined at several levels to cover then different facets, such as component consistency, compatibility or correctness. The article introduces multilevel contracts and a design+verification process for handling and analysing these contracts in component models. The approach is implemented with the COSTO platform that supports the Kmelia component model. A case study illustrates the overall approach.Comment: In Proceedings WCSI 2010, arXiv:1010.233

Business integration models in the context of web services.

E-commerce development and applications have been bringing the Internet to business and marketing and reforming our current business styles and processes. The rapid development of the Web, in particular, the introduction of the semantic web and web service technologies, enables business processes, modeling and management to enter an entirely new stage. Traditional web based business data and transactions can now be analyzed, extracted and modeled to discover new business rules and to form new business strategies, let alone mining the business data in order to classify customers or products. In this paper, we investigate and analyze the business integration models in the context of web services using a micro-payment system because a micro-payment system is considered to be a service intensive activity, where many payment tasks involve different forms of services, such as payment method selection for buyers, security support software, product price comparison, etc. We will use the micro-payment case to discuss and illustrate how the web services approaches support and transform the business process and integration model.