A Formal Diagrammatic Approach to Compensable Workflow Modelling

Workflows consist of interconnected tasks which are executed to achieve predefined business goals. When some tasks fail during execution, compensation can be used as an error-handling procedure to remove side-effects of already finished tasks. This paper extends our formal diagrammatic approach to workflow modelling (which uses principles from model-driven engineering (MDE)) to account for the phenomenon of compensation. Both static semantics, represented by instances of workflow models, and dynamic semantics, represented by a transition system, are described. In MDE, models are first class entities of the development process from which executable application code is generated. The use of MDE technologies is especially important for software in health services delivery where processes are safety critical, highly localised and frequently change.