Automata for Web Services Fault Monitoring and Diagnosis

Like any software, web service fault management is also required to go through different phases of fault management lifecycle. Model based diagnosis has been a well established practice for its several positive aspects including cognitively being better understood by development and testing teams. Automata is a simple and formally well defined model being used for monitoring and diagnosis of system faults. For the reason, here we have reviewed works on automata for web service fault management and also propose a model of stochastic automata for the purpose

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

Optimizing Computation of Recovery Plans for BPEL Applications

Web service applications are distributed processes that are composed of dynamically bounded services. In our previous work [15], we have described a framework for performing runtime monitoring of web service against behavioural correctness properties (described using property patterns and converted into finite state automata). These specify forbidden behavior (safety properties) and desired behavior (bounded liveness properties). Finite execution traces of web services described in BPEL are checked for conformance at runtime. When violations are discovered, our framework automatically proposes and ranks recovery plans which users can then select for execution. Such plans for safety violations essentially involve "going back" - compensating the executed actions until an alternative behaviour of the application is possible. For bounded liveness violations, recovery plans include both "going back" and "re-planning" - guiding the application towards a desired behaviour. Our experience, reported in [16], identified a drawback in this approach: we compute too many plans due to (a) overapproximating the number of program points where an alternative behaviour is possible and (b) generating recovery plans for bounded liveness properties which can potentially violate safety properties. In this paper, we describe improvements to our framework that remedy these problems and describe their effectiveness on a case study.Comment: In Proceedings TAV-WEB 2010, arXiv:1009.330

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)

Reconciling Web service failing interactions. Toward an approach based on automatic generation of mediators

International audienceInteractions between Web services are based on interfaces which describe Web services on both structural and behavioural perspectives. It can happen that the interface provided by a service does no longer match (for instance, because of an evolution) the interface required by its partners. In this situation, and until the required interfaces are fixed, interactions cannot succeed. To address this issue, and focusing on the behavioural part of interfaces, we propose an approach based on a mediator, automatically generated, which aims to seamlessly resolve incompatibilities during service interactions

A Software Tool for Selection and Integrability on Service Oriented Applications

Connecting services to rapidly developing service-oriented applications is a challenging issue. Selection of adequate services implies to face an overwhelming assessment effort, even with a reduced set of candidate services. On previous work we have presented an approach for service selection addressing the assessment of WSDL interfaces and the expected execution behavior of candidate services. In this paper we present a plugin for the Eclipse IDE to support the approach and to assist developers’ daily tasks on exploring services integrability. Particularly for behavioral compatibility we make use of two testing frameworks: JUnit and MuClipse to achieve a compliance testing strategy.Sociedad Argentina de Informática e Investigación Operativa (SADIO

Automata-Based Verification of Non-Functional Requirements in Web Service Composition

We address the problem of how to provide guarantees to a user that an automatically generated composition of independently developed web services meets the non-functional requirements (NFR). The user-specified NFR are in the form of hard constraints. We introduce an automata-based model for representing and reasoning about non-functional requirements for verifying the conformance to NFR. The approach described here enables this verification by lifting the NFR analysis from the level of individual services to the level of the search space of candidate compositions obtained from the functional requirements. The proposed approach can accommodate the different subsets of NFR for different components of a composite service. We introduce three different strategies when multiple NFRs exist and analyze their relative advantages and disadvantages under different scenarios. We present results which show that this approach to verifying the NFR can support efficient re-verification of web-service compositions whenever NFR are updated. The approach described here has been applied in service composition based on NFR in an Emergency Management System

Diagnosing and measuring incompatibilities between pairs of services

International audienceThis text presents a tool, from its design to its implementation, which detects all behavioural incompatibilities between two service interfaces. Unlike prior work, the proposed solution does not simply check whether two services are incompatible or not, it rather provides detailed diagnosis, including the incompatibilities and for each one the location in the service interfaces where these incompatibilities occur. A measure of similarity between interfaces which considers outputs from the detection algorithm is proposed too. A visual report of the comparison analysis is also provided which pinpoints a set of incompatibilities that cause a behavioural interface not to simulate another one

Analysis of communication models in web service compositions

In this paper we describe an approach for the verification of Web service compositions dened by sets of BPEL processes. The key aspect of such a verification is the model adopted for representing the communications among the services participating in the composition. Indeed, these communications are asynchronous and buffered in the existing execution frameworks, while most verication approaches assume a synchronous communication model for efficiency reasons. In our approach, we develop a parametric model for describing Web service compositions, which allows us to capture a hierarchy of communication models, ranging from synchronous communications to asynchronous communications with complex buffer structures. Moreover, we develop a technique to associate with a Web service composition the most adequate communication model, i.e., the simplest model that is sufficient to capture all the behaviors of the composition. This way, we can provide an accurate model of a wider class of service composition scenarios, while preserving as much as possible an efficient performance in verification