Integrating Transactions into BPEL Service Compositions

The Business Process Execution Language (BPEL) is now a de facto standard for specifying and executing business process for web service composition and orchestration. As more and more web services are composed using BPEL, tuning these compositions and gain better performance becomes increasingly important. This paper presents our approach for optimizing the BPEL process and introduces OptBPEL, a tool for performance optimization of BPEL process. The approach starts from the optimization of synchronization structure concerning link in BPEL. After that, some concurrency analysis techniques are applied to obtain further performance improvement. Finally, we give some experiments and prove the efficiency of these optimization algorithms used in OptBPEL.

The Business Process Execution Language (BPEL) has become the standard in Web service composition, so that been adopted by industries to create mission critical services. The business process reliability especially business process consistency when some services failed is critical to composite services especially involving various organizations. However, it is difficult to conduct business process reliability testing for composite services due to complex business process in service composition, remote deployed services and long time testing duration. Little research is done to test fault tolerance capabilities of composite services only from low level. This paper proposes a technique on how to test the reliability of composite service defined in BPEL from the view of business semantics with little cost using fault injection. We present an approach for reliability testing of web services by using service stubs with semantic faults instead of real services which can be placed at service provider side or service consumer side. Dislike existing studies, we focus on how to find the reliability problems associating with business process - called semantics as the problems are not pure coding error but faults related to business process. In addition, the behavior of composite services in BPEL is analyzed when there are faults in orchestrated services invoked. Finally, a case study is given to show the whole process of reliability testing for composite web service.

Business Process Execution Language (BPEL) has been popularly used to describe a collaborative business processes which is executed by Web services. However, the original BPEL language is defined in a strict format which the developers must follow. This leads to difficulties to create or modify the BPEL documents. In order to overcome the problem, the original BPEL has been extended to an annotated-BPEL so that BPEL documents can be freely modified. One of the applications of annotated-BPEL is that it is employed to describe "request" Web service information. Since Web service discovery systems may support different Web service description languages, annotated BPEL must be translated into specific description languages so that it can be readable and understood. This paper introduces a system that generates "request" Web services from the annotated BPEL. The system supports the two most popular Web services description languages, namely, OWL-S and WSDL. The description is first translated into OWL-S since it contains semantics in describing the service. This is done by searching 'the best matched' OWL concepts in a OWL repository and then filling these concepts into an predefined OWL-S template. If we cannot find any suitable concepts, a WSDL document will be generated.

RESTful Web service composition with BPEL for REST

Testing service orchestrations is a challenging research domain due to necessity of additional testing efforts, complementing traditional software testing. Although various testing approaches and tools have been proposed, most of them provide partial solutions covering single testing activities such as test path analysis, test case generation, Web service emulation, fault injection and so on. Following the current research direction, we have developed an integrated testing framework, called TASSA, which aims to provide end-to-end testing of Business Process Execution Language (BPEL) orchestrations. This paper introduces its core capability for automation of test cases generation, execution and management implemented in an open source tool for WSDL-based testing of both single Web services and composite Web services, described with BPEL. The tool's functionality includes identification of web service operations as well BPEL variables in case of service composition testing, generation of SOAP request templates, data driven testing, definition of assertions at different levels (HTTP, SOAP and BPEL variable), execution and management of test cases.

Service Oriented Architecture (SOA) has been widely used during the past decade due to its ability to seamlessly integrate various applications developed using different technologies. Web services based on open standards are the most commonly used technology to realize an SOA. Business processes are executed by appropriate orchestration of various services from different departments that belong to a single organization or from multiple organizations. Security is an important quality attribute that has to be built into any application that is developed using SOA. XML is the underlying technology for Web Service Description Language (WSDL), SOAP protocol and Business Process Execution Language (BPEL). It is highly probable that an attacker could inject malicious information into these XML files to modify the flow of the business process. Further, SOAP was not designed with security in mind, it is possible to tamper the SOAP messages while they are in transit. There exist a number of such potential vulnerabilities which lead to possible security breach in the individual services. In an orchestrated business process, there are possibilities of more vulnerabilities. One of the existing tools namely WS-Attacker is only capable of testing the security of individual web services alone. In spite of the widespread usage of SOA, currently there is limited automatic tool support for testing the security provided by an entire SOA application involving service orchestration. In this context, this paper focuses on designing and implementing a plug-in for WS-Attacker to analyze a few security vulnerabilities present in SOA business processes.

Problem statement: As distributed real-time multimedia services are accessed by users from different locations, the run-time performance must be managed and monitored to get a clear view of how media web services perform within their operational environments and to perform control actions to modify and adjust the their behavior. Otherwise it will provide negative effects on the reputation of service provider. Therefore the main objective of this study was to design and implement a media web service composed dynamically and to monitor the Dynamically Composed Media Web Services (DCMWS) through Parallel Performance Monitoring Service (PPMS). The PPMS is a web service that executed in parallel with media web service using multi threading technology. Approach: The PPMS monitors the run-time performance of Dynamically Composed Media Web Services (DCMWS) which were represented as BPEL (Business Process Execution Language) processes. The run-time performance of the media web services such as timeouts, external errors, percentage of successful completion of individual media web services and the occurrence of fault were monitored and using this result the corrective actions were taken by service providers. Results: The effectiveness of PPMS had been evaluated for media-on-demand composite web service and its results showed an improvement on the performance of run time monitoring of media web services. Conclusion: To facilitate management decisions and media web service behavior modifications, service providers need to monitor the run-time performance of DCMWS. In this context, the approach outlined in this study was most appropriate, convenient and efficient. The proposed PPMS herein played a crucial role in monitoring run-time performance of DCMWS.

Web services support software architectures that can evolve dynamically. In particular, in this paper the focus is on architectures where services are composed (orchestrated) through a workflow described in the business process execution language (BPEL). It is assumed that the resulting composite service refers to external services through assertions that specify their expected functional and non-functional properties. On the basis of these assertions, the composite service may be verified at design time by checking that it ensures certain relevant properties. Because of the dynamic nature of web services and the multiple stakeholders involved in their provision, however, the external services may evolve dynamically, and even unexpectedly. They may become inconsistent with respect to the assertions against which the workflow was verified during development. As a consequence, validation of the composition must extend to run time. In this work, an assertion language, called assertion language for BPEL process interactions (ALBERT), is introduced; it can be used to specify both functional and non-functional properties. An environment which supports design-time verification of ALBERT assertions for BPEL workflows via model checking is also described. At run time, the assertions can be turned into checks that a software monitor performs on the composite system to verify that it continues to guarantee its required properties. A TeleAssistance application is provided as a running example to illustrate our validation framework.

There are often three groups of experts involved in the design and implementation of business processes in a service oriented enterprise; business analysts, solution architects and system developers. They collaborate with each other to transform a high-level design created by a business analyst to a final executable workflow, based on a service composition language such as the Business Process Execution Language (BPEL). In this paper, we present a new approach to support and semi-automate this transformation process, thus producing applications of higher quality in shorter time. The idea is to capture existing knowledge in the enterprise, which is required for transforming models from one abstraction level to another, as reusable, parameterized patterns. These patterns are used for tool based model transformations of the business processes. To support our approach, we shall make use of Domain Specific Modeling Languages (DSMLs) designed for each enterprise to capture models of a business process at different levels of abstraction, each suitable for the use of one of the groups of experts. The presented approach bridges the gap between business and IT by providing customizable language-, tool- and transformation support for the different groups of experts within the enterprise and is illustrated by an example.

Web services technology is the most common implementation of service oriented architecture. Web services are based on open technologies such as eXtensible Markup Language (XML) and offer a distributed approach for the integration of heterogeneous applications across the internet. The process of combining web services functionalities into one composite service is called web services composition. To perform this task, several languages such as Business Process Execution Language (BPEL), Web Services Flow Language (WSFL) and Web Service Choreography Interface (WSCI) have emerged. These languages are based on programming concepts and neglect the specification step which is very important in any software development process. In this paper, we address the formal specification of web services descriptions and the modelling of their composition using the model driven engineering principles. To this end, we propose a domain specific language (DSL) called S-GNet. The proposed DSL introduces new modelling elements which make it well adapted to the web services characteristics. We also propose a graph grammar which transforms Web Services Description Language (WSDL) descriptions into their equivalent S-GNet specifications. This grammar is integrated within an S-GNet modelling tool.

This paper describes a method for the implementation and optimization of business processes in a service oriented architecture (SOA). A process specification is created by business people, and expressed in Business Process Modeling Notation (BPMN). The specification is then translated into Business Process Execution Language (BPEL), and used by technical people as a reference process, which is subject to a series of transformations that change the internal process structure in order to improve the quality of the process execution. The behavior of each transformed process is verified automatically against the behavior of the reference process. The verification mechanism is based on a mapping from BPEL to Language of Temporal Ordering Specification (LOTOS), followed by a comparison of the trace set that is generated using a program dependence graph of the reference process and the trace set of the transformed one. When the design goals have been reached, the transformed BPEL process can be executed on a target SOA environment using a BPEL engine.

Today, the Business Process Execution Language (BPEL) is the most emerging specification for Web Service Composition, which is an important part of the SOA paradigm. Defining a stateful communication protocol, BPEL enables potential for new security vulnerabilities. In this paper, we present a severe Denial-of-Service attack on a leading BPEL engine, illustrating new threats on availability in the context of BPEL. Derived from our observations, we developed a protection concept and implemented an application level firewall fending these types of attacks.

THE Internet, along with its related technologies, has created an interconnected world in which information flows easily and tasks are processed collaboratively. To make service-oriented applications more robust, Web services must be examined from a transactional perspective. By transactional, we mean first defining the actions that guide the execution of Web services when failures arise and then the states that permit claiming the success of this execution following the handling of these failures. A variety of transactional models are reported in the database community. Some of these models can be leveraged and enhanced in response to Web services characteristics while others are not suitable for Web services due to the dynamic nature of Web services, the long-running execution scenarios that Web services take part in, and the successful execution of Web services despite other peers’ failure. Today’s service-oriented applications require advanced transactional models that guarantee integrity and continuity of business processes despite the dynamic nature of the features of the environments hosting the execution of these applications. This special section sheds light on the latest advances in the fields of Web services and transactional models in order to better address advanced research on and experience with transactional Web services. Four papers out of 19 submissions were selected for inclusion in this special section. Each submission was subject to a double-review process by at least three peer reviewers. In the first paper, entitled “Event-Based Design and Runtime Verification of Composite Service Transactional Behavior,” Gaaloul et al. propose an event-driven approach to validate the transactional behavior of Web services taking part in compositions. A composition life cycle consists of four phases, namely, design, execution, monitoring, and reengineering. The verification of this behavior throughout this life cycle is done either at design time to validate recovery mechanisms’ consistency or after runtime to detect execution deviations and repair design errors, and, therefore, formally ensure the execution reliability of Web services. In addition, this verification is based on the Event Calculus formalism, which offers a sound definition for this reliability. In the second paper, entitled “FACTS: A Framework for Fault-Tolerant Composition of Transactional Web Services,” Liu et al. note that delivering reliable compositions over unreliable Web services is challenging. To address this challenge, Liu et al. identify a set of high-level exception handling strategies and a new taxonomy of transactional Web services to devise a fault-tolerant mechanism that combines exception handling and transaction techniques. In addition, Liu et al. devise two modules, known as specification and verification, to assist service designers in constructing fault handling logic conveniently and correctly. This logic is automatically injected into WS-BPEL. In the third paper, entitled “Rule-Based Coordination of Distributed Web Service Transactions,” von Riegen et al. study the distributed transactional activity control problem in the context of service choreographies. In such a context, many participants are allowed to work together to achieve a global, common goal, and the initiator of a process is not always the one who is able to commit or cancel a transaction. Von Riegen et al. introduce a framework that allows autonomous coordination of dynamic processes. This framework extends WSBusinessActivity to strengthen the role of the coordinator. Predicate rules are developed to let participants cancel or complete a process and help the coordinators decide on the completion processes and the confirmation or cancellation of the participants’ works. In the fourth paper, entitled “TQoS: Transactional and QoS-Aware Selection Algorithm for Automatic Web Service Composition,” El Haddad et al. focus on the issues of selecting and composing Web services. A design-time selection algorithm is proposed in which transactional and QoS requirements are both integrated into the selection process. This algorithm is based on the notion of risk that indicates if execution outcomes can either be compensated for or not. Two risk levels of execution in a transactional system are considered: Risk 0, meaning that if the execution is successful, the obtained outcomes can be compensated for by the user, and Risk 1, meaning that the system does not guarantee successful execution, but if it achieves it, the outcomes cannot be compensated for by the user. We hope this special section inspires researchers to develop new transactional models that would guarantee service-oriented applications integrity and continuity. 30 IEEE TRANSACTIONS ON SERVICES COMPUTING, VOL. 3, NO. 1, JANUARY-MARCH 2010

An emerging technology like business process execution language (BPEL) and its implementation in BPEL for Web services (BPEL4WS) gives extra possibilities in describing business processes. It further adheres, as a technology, in a consistent way to the underlying Web service-based implementation technology and is a perfect fit for service-oriented architectures (SOA) as they are currently implemented throughout organizations as a successor to enterprise application integration (EAI). However, BPEL4WS, in its current implementation, will only serve in a static way for production workflows. In this chapter we discuss how Semantic Web services through a semantic service-oriented architecture (SSOA) can be used to extend BPEL4WS to create ad hoc and collaborative workflows.

Business Process Execution Language (BPEL) is a widely recognized executable service composition language. Since BPEL integrates services of desired functionality to compose business processes, it is significantly different from typical programming languages. How to effectively locate the integration-level faults in BPEL programs is an open issue. In this paper, we propose the BPEL fault localization guidelines based on the characteristics of BPEL programs, and adapt Tarantula, a traditional fault localization technique, to locate the integration-level faults in BPEL programs. We also conducted an empirical study to demonstrate the feasibility of our methodology.