The emerging paradigm of electronic services promises to bring to distributed computation and services the flexibility that the web has brought to the sharing of documents. An understanding of fundamental properties of e-service composition is required in order to take full advantage of the paradigm. This paper examines proposals and standards for e-services from the perspectives of XML, data management, workflow, and process models. Key areas for study are identified, including behavioral service signatures, verification and synthesis techniques for composite services, analysis of service data manipulation commands, and XML analysis applied to service specifications. We give a sample of the relevant results and techniques in each of these areas.

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Abstract. We study the verification problem for e-service (and workflow) specifications, aiming at efficient techniques for guiding the construction of composite e-services to guarantee desired properties (e.g., deadlock avoidance, bounds on resource usage, response times). Based on previously proposed e-service frameworks such as AZTEC and e-FLow, decision flow language Vortex, and our early work on verifying Vortex specifications using model checking and infinite state verification tools, we introduce a very simple e-service model for our investigation of verification issues. We first show how three different model checking techniques are applied to verification of specifications in simple e-service model, where the number of processes is limited to a predetermined number. We then introduce pid quantified constraints, a new symbolic representation that can encode infinite system states, to verify systems with unbounded and dynamic process instantiations. We think that it is a versatile technique and more suitable for verification of e-service specifications. If this is combined with other techniques such as abstraction and widening, it is possible to solve a large category of interesting verification problems for e-services. 1

Designing and controlling cooperative applications composed from e-Services poses new and complex research problems. In the present paper, a model for specifying cooperative applications based on e-Services is proposed, which allows representing both statical and dynamic aspects of cooperating e-Services, and orchestration specifications in a dynamically evolving distributed environment. The characteristics of a run-time architecture for supporting flexible application executions are discussed. Substitution of e-Services with other ones with similar characteristics both at design-time and at run-time is discussed. Orchestration is performed without the need of centralized control on the flow of activities, thus allowing peer-to-peer interaction between cooperating organizations.

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Due to the distributed nature of modern composite web services, designers are facing new challenges in both requirement specification as well as logic validation. This paper proposes a top-down design/verification strategy that helps construct composite web services to meet preset system goals. The key to this approach is to specify desired global behaviors with a "conversation protocol" and verify preset system goals on the global protocol. Then peer implementations are synthesized from the conversation protocol. Three realizability conditions are provided to guarantee that the composition of synthesized peers will satisfy the previously verified system goals.

Abstract. There is great promise in the idea of having agent or web services available on the internet, that can be flexibly composed to achieve more complex services, which can themselves then also be used as components in other contexts. However it is challenging to realise this idea, without essentially programming the composition using some process language such as BPEL4WS or OWL-S process descriptions. This paper presents a mechanism for specifying the external interface to composite and component services, and then deriving an appropriate internal model to realise a functioning composition. We present a conversation specification language for defining interaction protocols and investigate the issue of synchronous and asynchronous communication between the composite service and the component services. The algorithm presented computes a valid orchestration of components, given the interface specification of the desired composite service, interface specifications of available components, and some mapping rules between parameters to deal with ontological issues. 1