An Automated Method for Web Service Orchestration Based on Reusable Building Blocks

Abstract

We describe a complete and largely automated method for the development of systems from web services, which comprises the encapsulation of services, as well as their composition, verification and subsequent implementation in a model-driven manner. The paper follows the steps of the method: In a first phase, we import WSDL descriptions automatically as UML 2.x activities and provide them as building blocks, with some optional, manual adaptations. In a second phase, these building blocks can be used to compose an application that orchestrates web services. The building blocks have behavioral contracts that enable automated, incremental verification based on compositional model checking. We demonstrate the approach by a subscription-based service to receive SMS messages.

Automated Encapsulation of UML Activities for Incremental Development and Verification

“…For the orchestration of web services, we demonstrated in [6] how WSDL descriptions can be imported automatically as activities. Each web service operation can be invoked by corresponding streaming parameter nodes.…”

“…2 takes care of authentication and optional re-sending in case of errors. This activity is part of our library for telecom services provided by the PATS laboratory operated by Telenor [14], further described in [6]. The activity is started via pin start, which invokes call behavior action a: Authenticate to retrieve authentication credentials from the Parlay-X server.…”

“…The surrounding system passes SMS messages to be sent out via streaming parameter node send. The actual sending happens via a web service call to a Parlay X server [13] within action s, which refers to a subordinate activity, taken from [6]. Since this invocation takes some time, SMS messages arriving in the meantime via send are stored in a buffer variable.…”

“…The numbers indicate that, in average, 71% of a system specification are contributed by reusable blocks from libraries. [6] 334 89 79% Treasure Hunt System [17] 131 73 64% Mobile Alarm System [7] 145 70 68% Embedded Sensor System [4] 144 75 71%…”

“…Those activities useful in several applications are stored together with their ESMs as self-contained building blocks in libraries for different domains. Currently, we have libraries for embedded sensor systems [4], trust management [5], and web service-based telecom services [6]. The method aims at a high degree of automation.…”