Model-Driven Development of Service Compositions: Transformation from Service Choreography to Service Orchestrations
University of Twente P.O. Box 217 7500 AE Enschede The Netherlands
By: Ravi Khadka Thesis for a degree in Master of Science in Computer Science University of Twente, Enschede, The Netherlands Graduation committee: dr. ir. Marten J. van Sinderen (UT- EEMCS) dr. Luis Ferreira Pires (UT-EEMCS) dr. ir. Brahmananda Sapkota (UT-EEMCS)
Enschede The Netherlands 2010
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Abstract
This thesis discusses the suitability of using model-driven transformation techniques to service composition and proposes a (semi-)automatic transformation that generates a set of related orchestrations from choreography. In this way we have contributed to the model-driven development of service composition. A service composition is an aggregation process that creates composite services from the existing ones. Service choreography and service orchestration are complementary viewpoints of service composition seen from different abstraction levels. This thesis investigates the architectural relationships between the service choreography and service orchestration and defines architectural patterns that capture their relationships. Based on these architectural patterns, we derive requirements for transformation specifications. We use modeldriven transformation techniques, in particular metamodel transformation that implies the definition of metamodels and the mapping between those metamodels. Hence, we develop metamodels for Web Service Choreography Definition Language (WS-CDL) and Web Service Business Process Execution Language (WS-BPEL) and define the transformation mappings between those metamodels. We define a transformation specification, which we derive from the architectural patterns, to implement the transformation mappings between the language constructs of WS-CDL and WS-BPEL. We implemented a transformation chain using metamodel transformation to transform a WS-CDL model to WS-BPEL process, as a proof-of-concept. We developed transformation rules using the transformation mappings that we defined earlier, and implemented them in Atlas Transformation Language (ATL). Due to the difference in abstraction levels between service choreography and service orchestration, the generated orchestration process requires some additional information not contained in the choreography specifications. We manually add this information to the transformation results. We used two application scenarios to validate our proof-of-concept. We validated our proof-of-concept in a pragmatic way by observing the behavior of the input choreography and checked if the behavior is shown by the generated BPEL process. Our proof-ofconcept shows that the service composition process can be accelerated by using model-driven transformation techniques. Further, we evaluated our proposed approach with three closely related developments that aim to transform a CDL specification to a BPEL process. Based on this comparison, our approach is proven to be the most promising.

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