Mohamed Graiet

Event-B Based Approach for Verifying Dynamic Composite Service Transactional Behavior

Verifying Web service composition in a dynamic environment remains one of the most difficult tasks despite the efforts and the previous proposed research works because new services can be composed during the execution step and others can automatically appear, disappear, or be updated. To achieve the Web service composition specification and verification, we introduce a new concept, called dynamic pattern. A dynamic pattern is an extension of a static one. Then, we propose to formalize dynamic Web Service composition in Event-B using dynamic patterns. The resulting model is progressively verified using proofs. We use animator of model (ProB) to detect a variety of problems, such as deadlocks or other unexpected behavior of a model.

Event-B Based Approach for Verifying Cloud Resource Allocation in Business Process

Cloud environments are being increasingly used for deploying and executing business processes to provide a high level of performance with low operating cost. Nevertheless, due to the lack of explicit and formal description of the resource perspective in existing business processes, cloud resources cannot be efficiently and optimally managed. The aim of the present paper is to offer a formal definition of the resource perspective in business processes as a step towards ensuring correct and optimal Cloud resource allocation in business process modeling. Concretely, we propose a formalism based on the Event-B for specifying Cloud resource allocation policies in business process models. This formal specification is used to formally validate the consistency of Cloud resource allocation for process modeling at design time, and to analyze and check its correctness according to users needs and resource properties. In order to show its feasibility, our approach has been tested using a real use case study from an industrial partner.

Verifying Composite Service Transactional Behavior with EVENT-B

A key challenge of Web Service (WS) composition is how to ensure reliable execution. Due to their inherent autonomy and heterogeneity, it is difficult to reason about the behavior of service compositions especially in case of failures. Therefore, there is a growing interest for verification techniques which help to prevent service composition execution failures. In this paper, we present a proof and refinement based approach for the formal representation, verification and validation of Web Services transactional compositions using the Event-B method.

Towards correct cloud resource allocation in business processes

Cloud environments are being increasingly used for deploying and executing business processes to provide a high level of performance with low operating cost. Nevertheless, due to the lack of an explicit and formal description of the resource perspective in the existing business processes, the correctness of Cloud resources management can not be verified. The aim of the present work is to offer a formal definition of the resource perspective in business processes as a step towards ensuring a correct and consistent Cloud resource allocation in business process modeling. Concretely, we propose a formalism based on the Event-B language for specifying Cloud resource allocation policies in business process models. This formal specification is used to formally validate the consistency of Cloud resource allocation for process modeling at design time, and to analyze and check its correctness according to user requirements and resource capabilities. In order to show its feasibility, our approach has been tested using a real use case study from an industrial partner.

Event-B Formalisation of Web Services for Dynamic Composition

The capacity of a composite service to change configuration according to the component services behavior is essential. In particular, this reconfiguration should be done dynamically without disturbing the service execution. To the best of our knowledge, few works were interested in verifying the coherence of this dynamic reconfiguration. By dynamic reconfiguration we mean for example, overcome the failure or the unavailability of a service component by the the discovery and the replacement of another service that provides the same functionalities. But, the new service may have the same structure but provide additional features that can make the composite service not behaving as expected. To do so, we propose an approach based on Event-B for a formal verification of the structural and behavioral properties of the component service before dynamically integrated into the composition during the execution.

Towards an approach of formal verification of mediation protocol based on web services

SOA (Service Oriented Architecture) defines a new Web services cooperation paradigm in order to develop distributed applications using reusable services. The handling of such collaboration has different problems that lead to many research efforts. In this paper, we address the problem of Web service composition. Indeed, various heterogeneities can arise during the composition. The resolution of these heterogeneities, called mediation, is needed to achieve a service composition. In this paper, we propose a sound approach to formalize Web services composition mediation with the ADL (Architecture Description Language) ACME. To do so, we first model the meta model of composite service manager and mediation. Then we specify semi formal properties associated with this meta model using OCL (Object Constraint Language). Afterwards, we formalize the mediation protocol using Armani, which provides a powerful predicate language in order to ensure service execution reliability.

A Formal Approach for Enforcing Transactional Requirements in Web Service Compositions

Service based applications leveraging different features are today the underpinnings of enterprise computing. However, current Web services composition systems make only use of functional requirements in the selection process of component Web services while transactional consistency is a crucial parameter of most business applications. In this work, we propose a formal approach for enforcing transactional requirements in Web service compositions using Event-B formalism. Our solution enables specifying composite Web services where partner Web services are selected at runtime according to the transactional requirements that are defined based on the Acceptable Termination States concept. The resulting composite Web service is compliant with the consistency requirements expressed by business application designers. Moreover, we incrementally combine proof based models with model checking to trace possible errors and then come back to make proofs of the proof obligations.

Formal Verification of SCA Assembly Model with Event-B

Service Component Architecture (SCA) is a new promising programming model for constructing service-oriented application, which facilitates the development of business integration in SOA. However, SCA in its current form does not represent any formal definition. In addition, there is a growing interest for verification techniques which help to prevent SCA composition specification failure. In this paper, firstly, we present an Event-B model for formal representation and verification of an SCA based composition. And then, we extend this model in order to automate the transformation and the verification of the SCA assembly by the implantation of an Eclipse plug-in.

Towards an approach of formal verification of mediation protocol based on web services of MDE type

Purpose – The purpose of this paper is to formally verify the composition of web services to reduce inconsistencies in software architectures.Design/methodology/approach – In order to check the web services composition, the authors use a model‐driven engineering (MDE)‐based approach and to achieve the formalization of web service composition in ACME and check the consistency of this composition, the authors introduce the pattern mediation to formalize web services composition with the ADL ACME, using the concept of architectural style of ACME. Subsequently, a scenario shows how this style can be used in ACMEStudio to detect inconsistencies. The example shows a web travel organization application.Findings – The authors ensure reliability defined through non‐functional properties. To do so, use ACME was used to check assembling consistency of web service composition. In a second part, a SWC2ACME tool was designed and implemented to check if the web services meta‐model conforms to ACME model.Originality/valu...

An Event-B Based Approach for Ensuring Correct Configurable Business Processes.

A configurable process model captures a family of similar processes. Such models can be configured to obtain a process variant according to specific requirements. With this aim, several approaches have been proposed for the configuration of process models. Nevertheless, an increasing attention is being paid to achieve this in a sound manner due to the complex inter-dependencies between the configuration decisions. In this work, we aim to guide the process analyst to easily configure process models while preserving soundness. To do so, we propose a formal approach for ensuring correctness of business process configurations while considering structural constraints they have to obey. Specifically, using the Event-B language, we formally define a configurable process model, its correctness-preserving conditions and its configuration constraints.