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)

Verifying service continuity in a satellite reconfiguration procedure: application to a satellite

The paper discusses the use of the TURTLE UML profile to model and verify service continuity during dynamic reconfiguration of embedded software, and space-based telecommunication software in particular. TURTLE extends UML class diagrams with composition operators, and activity diagrams with temporal operators. Translating TURTLE to the formal description technique RT-LOTOS gives the profile a formal semantics and makes it possible to reuse verification techniques implemented by the RTL, the RT-LOTOS toolkit developed at LAAS-CNRS. The paper proposes a modeling and formal validation methodology based on TURTLE and RTL, and discusses its application to a payload software application in charge of an embedded packet switch. The paper demonstrates the benefits of using TURTLE to prove service continuity for dynamic reconfiguration of embedded software

Analysis and representation of test cases generated from LOTOS

Cataloged from PDF version of article.This paper presents a method to generate, analyse and represent test cases from protocol specification. The language of temporal ordering specification (LOTOS) is mapped into an extended finite state machine (EFSM). Test cases are generated from EFSM. The generated test cases are modelled as a dependence graph. Predicate slices are used to identify infeasible test cases that must be eliminated. Redundant assignments and predicates in all the feasible test cases are removed by reducing the test case dependence graph. The reduced test case dependence graph is adapted for a local single-layer (LS) architecture. The reduced test cases for the LS architecture are enhanced to represent the tester's behaviour. The dynamic behaviour of the test cases is represented in the form of control graphs by inverting the events, assigning verdicts to the events in the enhanced dependence graph. © 1995

Automated Analysis and Implementation of Composed Grid Services

Service composition allows web services to be combined into new ones. Web service composition is increasingly common in mission-critical applications. It has therefore become important to verify the correctness of web service composition using formal methods. The composition of grid services is a similar but new goal. We have previously developed an abstract graphical notation called CRESS for describing composite grid services. We have demonstrated that it is feasible to automatically generate service implementations as well as formal specifications from CRESS descriptions. The automated service implementations use orchestration code in BPEL, along with the service interfaces and data types in WSDL and XSD respectively for all services. CRESS-generated BPEL implementations currently do not useWSRF features such as implicit endpoint references for WS-Resources and interfacing to standard WSRF port types. CRESS-generated formal models use the standardised process algebra LOTOS. Service behaviour is modelled by processes, while service data types are modelled as abstract data types. Simulation and validation of the generated LOTOS specifications can be performed. In this paper, we illustrate how CRESS can be further extended to improve its generation of service compositions, specifically for WSRF services implemented using Globus Toolkit 4. We also show how to facilitate use of the generated LOTOS specifications with the CADP toolbox

Analysis and Verification of Service Interaction Protocols - A Brief Survey

Modeling and analysis of interactions among services is a crucial issue in Service-Oriented Computing. Composing Web services is a complicated task which requires techniques and tools to verify that the new system will behave correctly. In this paper, we first overview some formal models proposed in the literature to describe services. Second, we give a brief survey of verification techniques that can be used to analyse services and their interaction. Last, we focus on the realizability and conformance of choreographies.Comment: In Proceedings TAV-WEB 2010, arXiv:1009.330

An Integrated Methodology for Creating Composed Web/Grid Services

This thesis presents an approach to design, specify, validate, verify, implement, and evaluate composed web/grid services. Web and grid services can be composed to create new services with complex behaviours. The BPEL (Business Process Execution Language) standard was created to enable the orchestration of web services, but there have also been investigation of its use for grid services. BPEL specifies the implementation of service composition but has no formal semantics; implementations are in practice checked by testing. Formal methods are used in general to define an abstract model of system behaviour that allows simulation and reasoning about properties. The approach can detect and reduce potentially costly errors at design time. CRESS (Communication Representation Employing Systematic Specification) is a domainindependent, graphical, abstract notation, and integrated toolset for developing composite web service. The original version of CRESS had automated support for formal specification in LOTOS (Language Of Temporal Ordering Specification), executing formal validation with MUSTARD (Multiple-Use Scenario Testing and Refusal Description), and implementing in BPEL4WS as the early version of BPEL standard. This thesis work has extended CRESS and its integrated tools to design, specify, validate, verify, implement, and evaluate composed web/grid services. The work has extended the CRESS notation to support a wider range of service compositions, and has applied it to grid services as a new domain. The thesis presents two new tools, CLOVE (CRESS Language-Oriented Verification Environment) and MINT (MUSTARD Interpreter), to respectively support formal verification and implementation testing. New work has also extended CRESS to automate implementation of composed services using the more recent BPEL standard WS-BPEL 2.0

The formal, tool supported development of real time systems

The language SDL has long been applied in the development of various kinds of systems. Real-time systems are one application area where SDL has been applied extensively. Whilst SDL allows for certain modelling aspects of real-time systems to be represented, the language and its associated tool support have certain drawbacks for modelling and reasoning about such systems. In this paper we highlight the limitations of SDL and its associated tool support in this domain and present language extensions and next generation real-time system tool support to help overcome them. The applicability of the extensions and tools is demonstrated through a case study based upon a multimedia binding object used to support a configuration of time dependent information producers and consumers realising the so called lip-synchronisation algorithm