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a b s t r a c tCurrent Web service technology is evolving towards a simpler approach to define Web service APIs that challenges the assumptions made by existing languages for Web service composition. RESTful Web services introduce a new kind of abstraction, the resource, which does not fit well with the message-oriented paradigm of the Web service description language (WSDL). RESTful Web services are thus hard to compose using the Business Process Execution Language (WS-BPEL), due to its tight coupling to WSDL. The goal of the BPEL for REST extensions presented in this paper is twofold. First, we aim to enable the composition of both RESTful Web services and traditional Web services from within the same process-oriented service composition language. Second, we show how to publish a BPEL process as a RESTful Web service, by exposing selected parts of its execution state using the REST interaction primitives. We include a detailed example on how BPEL for REST can be applied to orchestrate a RESTful e-Commerce scenario and discuss how the proposed extensions affect the architecture of a process execution engine.

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RESTful Web services are software services which are published on the Web, taking full advantage and making correct use of the HTTP protocol. This chapter gives an introduction to the REST architectural style and how it can be used to design Web service APIs. We summarize the main design constraints of the REST architectural style and discuss how they impact the design of so-called RESTful Web service APIs. We give examples on how the Web can be seen as a novel kind of software connector, which enables the coordination of distributed, stateful and autonomous software services. We conclude the chapter with a critical overview of a set of emerging technologies which can be used to support the development and operation of RESTful Web services.

Whereas a consensus has been reached on defining the set ofworkflow patterns for business process modeling languages, no such patterns existsfor workflows applied to scientific computing on the Grid By looking at different kinds ofparallelism, in this paper we identify a set ofworkflow patterns related to parallel and pipelined execution. The paper presents how these patterns can be represented in different Grid workflow languages and discusses their implications for the design of the underlying workflow management and execution infrastructure. A preliminary classification ofthese patterns is introduced by surveying how they are supported by several existing advanced scientific and Grid workflow languages.

Abstract. The REST architectural style is emerging as an alternative technology platform for the realization of service-oriented architectures. In this paper, we apply the notion of composition to RESTful services and derive a set of language features that are required by composition languages for RESTful services: dynamic late binding, dynamic typing, content-type negotiation, state inspection, and compliance with the uniform interface principle. To show how such requirements can be satisfied by an existing composition language, we include a case-study using the JOpera visual composition language. In it, we present how to build a composite application (DoodleMap) out of some well-known, public and currently existing RESTful service APIs.