Temporal Exception in Web Service Composition

FRWSC: a framework for robust Web service composition

The deployment of Web services in a highly dynamic environment brings about a number of research challenges. In dynamic Web services composition, failures and changes to atomic services cannot be detected before invocation. Hence, the failure or even the change in an atomic service may lead to the overall failure of the composite service. In addition, SOAP error code is not sufficient for the client to analyze the failure reason and handle it. In this work, we introduce a framework to deal with unexpected failures during runtime composition. The proposed framework is built on top of composite services stack as an interface between the composite service and its external service partners. The evaluation results show that by using the proposed framework, it is possible to avoid composite service failures that are caused by changes or failures in atomic services.

Polibits, 2014

This paper presents an approach for modeling and associating Policies to services' based applications. It proposes to extend the SOD-M model driven method with (i) the ⇡-SCM, a Policy services' composition meta-model for representing non-functional constraints associated to services' based applications; (ii) the ⇡-PEWS meta-model providing guidelines for expressing the composition and the policies; and, (iii) model to model and model to text transformation rules for semi-automatizing the implementation of reliable services' compositions. As will be shown within our environment implementing these meta models and rules, one may represent both systems' cross-cutting aspects (e.g., exception handling for describing what to do when a service is not available, recovery, persistence aspects) and constraints associated to services, that must be respected for using them (e.g., the fact that a service requires an authentication protocol for executing a method).

2009

Web services are becoming progressively popular in the building of both inter-and intra-enterprise business processes. These processes are composed from existing Web services based on defined requirements. In collecting together the services for such a composition, developers can employ languages and standards for the Web that facilitate the automation of Web service discovery, execution, composition and interoperation. However, there is no guarantee that a composition of even very good services will always work.

2001

In this position paper, we present our work on Web services with multiple classes of service, called service offerings, and on management and dynamic (i.e., runtime) adaptation of their compositions. We explain the motivation for Web services with multiple service offerings, present some management and dynamic adaptation algorithms based on the manipulation of provided service offerings, and discuss some of the issues with the corresponding management infrastructure, called DAMSC (Dynamically Adaptable and Manageable Service Components), that we are developing. We also briefly present our work on WSOL (Web Service Offerings Language) -an extension of WSDL (Web Services Description Language) that enables specification of various types of constraints-including functional, nonfunctional (QoS -Quality of Service), authorization policies, etc.-and specification of Web services with multiple service offerings. At the end, we summarize some of the challenges for future research in the area of management and dynamic adaptation of compositions of Web services.

Proceedings of the 2007 Workshop on Engineering Fault Tolerant Systems, EFTS '07, 2007

Many businesses are now moving towards the use of composite web services that are based on a collection of web services working together to achieve an objective. Although they are becoming business-critical elements, current development support tools do not provide a practical way to include fault tolerance characteristics in web services compositions. This paper proposes a mechanism that allows programmers to easily develop fault tolerant compositions using diverse web services. The mechanism allows programmers to specify alternative web services for each operation and offers a set of artifacts that simplify the coding process, by automatically dealing with all the aspects related to the redundant web services invocation and responses voting. The mechanism is also able to perform a continuous evaluation of the services based on their behavior during operation. The approach is illustrated using compositions based on web services publicly available in the Internet and on the web services specified by the standard TPC-App performance benchmark.

2008

Many businesses are now moving towards the use of composite web services. These consist of a collection of web services working together to achieve an objective. Although they are becoming business-critical elements, current development tools do not provide a practical way to include fault tolerance characteristics in web services compositions. This paper proposes a mechanism that allows programmers to easily develop fault tolerant compositions using diverse services. The mechanism allows programmers to specify alternative web services for each operation and offers a set of artifacts that simplify the coding process, by automatically dealing with all aspects related to the redundant web services invocation and responses voting. The mechanism is also able to perform a continuous evaluation of the services based on their behavior during operation. The approach is illustrated using compositions based on services publicly available in the Internet and on the services specified by the standard TPC-App performance benchmark.

Lecture Notes in Computer Science, 2009

Decentralized orchestration offers performance improvements in terms of increased throughput and scalability and lower response time. However, decentralized orchestration also brings additional complexity to the system, mainly, in terms of exception handling. The research presented in this paper is carried out on the basis of some previous work of the authors, including: decentralizing orchestration of composite Web services and exception handling. We focus also on current works expanding the previous one, exhibiting thus a higher performance degree which the integration of mobile agents performs by moving the application's functionality through the network. amongst the business partners are transferred and processed by the coordinator. Accordingly, the communication overload is relatively high and in some cases, the centralized coordinator becomes a bottleneck limiting so the scalability of the system. There are also arguments that this model is not flexible enough for scenarios where data flow has to be transported in a given path due to certain business constraints [6]. Starting from the intention to overcome these drawbacks, some decentralized solutions [7, 8, 9, 10, 12, 13] have been proposed. A second key problem that we can identify in process-oriented composition languages like BPEL concerns support for dynamic adaptation of the composition logic. Such languages assume that the composition logic is predefined and static, an assumption that does not hold in the highly dynamic context of web services. In fact, new web services are offered and others disappear quite often. In addition, the organizations involved in a web service composition may change their business rules, partners, and collaboration conditions. Furthermore, software, machine or communication link failures may render certain sub-process of composite services unavailable, precluding thus the successful execution of the business process. Therefore, services-based systems are inherently vulnerable to exceptions. In these cases, a replacement component should be identified and substituted for the failed one. The replacement component should have the same skills to the later i.e. to have same functionality and QoS [2]. Note that due to the static nature of BPEL, which dictates that service bindings should be hard-coded in the scenario, it is not feasible to include calls to all replacement services within a fault handler (typically 2 or 3 alternates will be specified [3]) and not possible at all to dynamically introduce new bindings or remove Mounira ILAHI LI3 Member

IEICE Transactions on Information and Systems, 2010

In this paper, we propose a novel Web service composition framework which dynamically accommodates various failure recovery requirements. In the proposed framework called Adaptive Failure-handling Framework (AdaFF), failure-handling submodules are prepared during the design of a composite service and some of them are systematically selected and combined with the composite Web service at runtime in accordance with the requirement of individual users. In contrast, existing frameworks cannot adapt the failure-handling behaviors to user's requirements. AdaFF rapidly delivers a composite service supporting adaptive failure handling without manual development, and contributes to a flexible composite Web service design in that service architects never care about failure handling or variable requirements of users. For proof of concept, we implement a prototype system of the AdaFF, which automatically generates a composite service instance with Web Services Business Process Execution Language (WS-BPEL) according to the users' requirement specified in XML format, and executes the generated instance on the ActiveBPEL engine.

Journal of the Brazilian Computer Society, 2012

The Service Component Architecture (SCA) makes it possible to combine existing and new services based on a variety of technologies with components built using a component-based development approach. However, when asynchronous service compositions are executed, one or more errors can occur, possibly at the same time, affecting the dependability of the composition. To guarantee that the composition succeeds or at least fails in a controlled manner, fault tolerance mechanisms must be employed. In this paper, we propose a novel exception handling model that targets the needs of dependable SCA applications. The model is applicable to service-oriented systems and allows the creation of fault-tolerant asynchronous service compositions. The EH-SCA framework instantiates the proposed model as an extension of the Apache Tuscany SCA infrastructure. Developers can apply this instantiation of the model to both new and existing applications by using a simple and flexible aspect-oriented programming model. Finally, a case study of the EH-SCA framework shows how it can be used to build dependable distributed applications.

2006

The interest surrounding the Web services (WS) composition issue has been growing tremendously. In the near future, it is awaited to prompt a veritable shift in the distributed computing history, by making the Service-Oriented Architecture (SOA) a reality. Yet, the way ahead is still long. A careful investigation of a major part of the solutions proposed so far reveals that they follow a workflow-like composition approach and that they view failures as exceptional situations that need not to be a primary concern. In this paper, we claim that obeying these assumptions in the WS realm may constrain critically the chances to achieve a high-dependability level and may hamper significantly flexibility. Motivated with these arguments, we propose a WS composition modeling approach that accepts failures inevitability and enriches the composition with concepts that can add flexibility and dependability but that are not part from the WS architecture pillars, namely, the state, the transactional behavior, the vitality degree, and the failure recovery. In addition, we describe a WS composition in terms of definition rules, composability rules, and ordering rules, and we introduce a graphical and a formal notation to ensure that a WS composition is easily and dynamically adaptable to best suit the requirements of a continuously changing environment. Our approach can be seen as a higher level of abstraction of many of the current solutions, since it extends them with the required support to achieve higher flexibility, dependability, and expressiveness power.

Web services are gaining importance and are often used as a standard approach for integrating diverse miscellaneous services often distributed over the network. Hence, it necessitates attaining high levels of reliability and availability without being affected by any service, network or infrastructure failures. To accomplish this, we propose an efficient mechanism which will narrow the plausibility of fault detection by dynamic web service selection among similar services. The Quality-of-service (QoS) can have an important effect on web service composition service reliability. In this paper, we perceive the rationale for the failure of the web services and resolve it by considering the QoS attributes like response time, execution time, etc. The proposed modeling approach indicates a possible reduction in the failure probability as well as a significant improvement in the execution duration of the complex web services composition. This has been proved through the results achieved with an experimental setup.

2003

The recent evolution of internet technologies, mainly guided by the Extensible Markup Language (XML) and its related technologies, are extending the role of the World Wide Web from information interaction to service interaction. This next wave of the internet era is being driven by a concept named Web services. The Web services technology provides the underpinning to a new business opportunity, i.e., the possibility of providing value-added Web services. However, the building of value-added services on this new environment is not a trivial task. Due to the many singularities of the Web service environment, such as the inherent structural and behavioral heterogeneity of Web services, as well as their strict autonomy, it is not possible to rely on the current models and solutions to build and coordinate compositions of Web services. In this paper, we present a framework for building reliable Web service compositions on top of heterogeneous and autonomous Web services.

2006

Current Web services composition approaches do not take into account transactional requirements defined by designers. The transactional challenges raised by the composition of Web services are twofold: relaxed atomicity and dynamicity. In this paper, we propose a new process to automate the design of transactional composite Web services. Our solution enables the composition of Web services not only according to functional requirements but also to transactional ones defined using the Acceptable Termination States model. The resulting composite Web service is compliant with the consistency requirements expressed by designers and its execution can easily be coordinated using the coordination rules provided as an outcome of our approach.

2006

The dynamic nature of the Web imposes the automation of web service compositions. Since these compositions serve high level business purposes, it is mandatory to address the reliability issue. The autonomic computing paradigm, introduced by IBM, offers a guideline for building self-managing systems. An important principle of this paradigm is the self-healing behaviour which represents the ability of a system to recover from faulty situations. This paper investigates how to increase the reliability of automatic web service compositions by proposing a framework for adding self-healing behaviour. First, we analyze the general domain of autonomic web services and then, we propose a formal description and architecture for adding self-healing behaviour to web service compositions.

Emerging Web Services Technology, Volume II, 2008

Several works have addressed the management of individual Web Services. However, the specific management requirements of workflow-based web service compositions such as those specified in the BPEL have not yet been considered. In this paper, we present several management requirements in web service compositions such as discovery and selection management, SLA and policy management, middleware services management, and management of the composite service. Supporting these requirements is crucial for providing a reliable service composition with well-defined QoS properties. We also introduce web service composition management and present our vision of having dedicated tool support for it in future BPEL engines.