In a Service-Oriented Architecture (SOA), a system is viewed as a collection of independent units (services) that interact with one another through message exchanges. Established languages such as the Web Services Description Language and the Business Process Execution Language allow developers to capture the interactions in which an individual service can engage, both from a structural and from a behavioral perspective. However, in large serviceoriented systems, stakeholders may require a global picture of the way services interact with each other, rather than multiple small pictures focusing on individual services. Such “global models ” are especially useful when a set of services interact in such a way that none of them sees all messages being exchanged, yet interactions taking place between some services affect the way other services interact. An issue that arises when dealing with global models of service interactions is that these models may capture behavioral constraints that can not be enforced locally. In other words, some global models may not be translatable into a collection of local models such that the sum of the local models equals the original global model. Starting from a previously proposed language for global modeling of service interactions, this paper defines an algorithm for determining if a global model is locally enforceable and an algorithm for generating local models from global ones. 1

Abstract. Choreographies offer means to capture global interactions between business processes of different partners. BPEL4Chor has been introduced to describe these interactions using BPEL. Currently, there are no formal methods available to verify BPEL4Chor choreographies. In this paper, we present how BPEL4Chor choreographies can be verified using Petri nets. A case study undermines that our verification techniques scale. Additionally, we show how the verification techniques can be used to generate a stub process for a partner taking part in a choreography. This is especially useful when the behavior of one participant is intended to follow the corresponding requirements of the other participants. Thus, the missing participant behavior can be generated and the error-prone design of that participant can be skipped.

Abstract. A fundamental promise of service oriented architecture (SOA) lies in the ease of integrating sharable information, processes, and other resources through interactions among the shared components that are modeled as web services. It is expected that not only the participating services are complex and have observable states, but the number of interacting services may be also large. Prior work on choreographies (conversation protocols) all focuses on specifying how the interacting web services should behave globally. Studies have shown that the relationships between global and local specifications of service interactions could be rather intricate. In this paper, we formulate a framework consisting of logical and implementation levels. We survey and discuss the technical problems and known results concerning service design, analysis and verification in this framework. 1

Abstract. In this paper we present a framework for describing a series of pattern variants encountered in the context of Service Interaction. The original Service Interaction Patterns [9] only covered 13 interactions scenarios. Moreover, some important aspects of service interaction of a bilateral and multilateral nature are not addressed in [9]. Furthermore, these patterns allow for ambiguous interpretation due to the absence of a formal semantics. The scope of the patterns generated by means of the framework described in this paper is much broader. To avoid ambiguities we formalize the semantics of the patterns by means of Colored Petri Nets (CPN). In addition, we propose an intuitive graphical notation that can be used to denote the various pattern variants. This paper also provides an evaluation of WS-BPEL v2.0 standard using these patterns.

Abstract. In Service-Oriented Computing (SOC), fragmentation and merging of workflows are motivated by a number of concerns, among which we can cite design issues, performance, and privacy. Fragmentation emphasizes the application of design and runtime methods for clustering workflow activities into fragments and for checking the correctness of such fragment identification w.r.t. to some predefined policy. We present a fragment identification approach based on sharing analysis and we show how it can be applied to abstract workflow representations that may include descriptions of data operations, logical link dependencies based on logical formulas, and complex control flow constructs, such as loops and branches. Activities are assigned to fragments (to infer how these fragments are made up or to check their well-formedness) by interpreting the sharing information obtained from the analysis according to a set of predefined policy constraints. 1

Developing cross-organizational business processes is a tedious task. The partners have to agree on a common data format and meaning as well as on the Quality of Service (QoS) requirements each partner has to fulfill. The QoS requirements are typically described using Service Level Agreements (SLAs) among the partners. In this paper, we propose a top-down modeling approach for Web service based business processes to capture the functional and non-functional aspects using a choreography language (WS-CDL) which describes the message interactions among the participants. The choreography is annotated with SLAs for the different partners. For each partner in the process, an orchestration (in WS-BPEL) and the necessary Web service templates are automatically generated. Additionally, the Service Level Objectives (SLOs) from the partner SLAs are automatically translated into policies which can then be enforced by a BPEL engine during execution. 1.

Abstract. Organizations, to function effectively and expand their boundaries, require a deep insight into both process orchestration and choreography of cross-organization business processes. The set of requirements for service interactions is significant, and has not yet been sufficiently refined. Service Interaction Patterns studies by Barros et al. demonstrate this point. However, they overlook some important aspects of service interaction of bilateral and multilateral nature. Furthermore, the definition of these patterns are not precise due to the absence of a formal semantics. In this paper, we analyze and present a set of patterns formed around the subset of patterns documented by Barros et al. concerned with Request-Reply interactions, and extend these ideas to cover multiple parties and multiple messages. We concentrate on the interaction between multiple parties, and analyze issues of a non-guaranteed response and different aspects of message handling. We propose one configurable, formally defined, conceptual model to describe and analyze options and variants of request-reply patterns. Furthermore, we propose a graphical notation to depict every pattern variant, and formalize the semantics by means of Coloured Petri Nets. In addition, we apply this pattern family to evaluate WS-BPEL v2.0 and check how selected pattern variants can be operationalized in Oracle BPEL PM. 1

Abstract—Service-oriented workflows in the scientific domain are commonly composed as Directed Acyclic Graphs (DAGs), formed from a collection of vertices and directed edges. When orchestrating service-oriented DAGs, intermediate data are typically routed through a single centralised engine, which results in unnecessary data transfer, increasing the execution time of a workflow and causing the engine to become a performance bottleneck. This paper introduces an architecture for deploying and executing service-oriented DAG-based workflows across a peerto-peer proxy network. A workflow is divided into a set of vertices, disseminated to a group of proxies and executed without centralised control over a peer-to-peer proxy network. Through a Web services implementation, we demonstrate across PlanetLab that by reducing intermediate data transfer, end-to-end workflows are sped up. Furthermore, our architecture is non-intrusive: Web services owned and maintained by different institutions do not have to be altered prior to execution. I.

ter verkrijging van de graad van doctor aan de Universiteit Twente, op gezag van de rector magnificus, prof.dr. H. Brinksma, volgens besluit van het College voor Promoties in het openbaar te verdedigen

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