Business Process Execution Language (BPEL) is an XML-based Web service composition language that is commonly used for the orchestration of business processes. Orchestration refers to the sequencing of services, usually defined in a separate Web Services Definition Language (WSDL) document, in order to provide additional logic to process data, which essentially creates the application logic. In certain situations, when business goals or policies change, these services (external to the orchestrated process) may change in a way that it affects the orchestrated process. For example, some services may be removed and new ones introduced. In situations like this, BPEL models need to be changed accordingly. In large and complex business processes, due to the verbose nature of BPEL, making alterations to BPEL descriptions is an arduous task, and can often lead to inconsistencies and errors. This paper demonstrates a way to map BPEL processes and related WSDL service descriptions into algebraic expressions, which encapsulate all process elements into a single phrase. The purpose of these algebraic expressions is to easily identify the effect of service changes in the orchestrated process, which in turn enables the required changes to be carried out efficiently in-situ within a given context, without disturbing the consistency of the overall BPEL document The proposed algebraic methodology is based on Kleene Algebra with Tests (KAT), which is a new branch of algebra that lends itself for practical modeling purposes.
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