Data-bound variables for WS-BPEL executable processes

Abstract

Standard BPEL (Business Process Execution Language) variables, if used to store the data from a data store, cannot be automatically synchronized with the data source in case other applications change the data during the BPEL process execution, which is a common occurrence particularly for long-running BPEL processes. BPEL also does not provide a mechanism for active monitoring of changes of data that would support automated detection and handling of such changes. This paper proposes a new type of BPEL variables, called data-bound variables. Data-bound variables are automatically synchronized with the data source and thus eliminate the need to implement data synchronization manually. To provide support for data-bound variables, we propose specific extensions to BPEL and the use of appropriate Data Access Services (DAS) that act as data providers. We introduce new BPEL activities to load, create and delete remote data. We also introduce observed properties, observed property groups and a variable handler. Using this mechanism, the BPEL process is able to automatically adapt to changes to data, made inside or outside the process scope, by following the Event, Condition, Action (ECA) paradigm. As a proof-of-concept, we have developed a prototype implementation of our proposed BPEL extensions and tested it by implementing three pilot projects. We have confirmed that our proposed solution decreases BPEL process size and complexity, increases readability and reduces semantic gap between BPMN process model and BPEL.