Imperative versus Declarative Process Variability: Why Choose?

Variability is a powerful abstraction in software engineering that allows managing product lines and business processes requiring great deals of change, customization and adaptation. In the field of Business Process Management (BPM) the increasing deployment of workflow engines having to handle an increasing number of instances has prompted for the strong need for variability techniques. The idea is that parts of a business process remain either open to change, or not fully defined, in order to support several versions of the same process depending on the intended use or execution context. The goal is to support two major challenges for BPM: re-usability and flexibility. Existing approaches are broadly categorized as Imperative or Declarative. We propose Process Variability through Declarative and Imperative techniques (PVDI), a variability framework which utilizes temporal logic to represent the basic structure of a process, leaving other choices open for later customization and adaptation. We show how both approaches to variability excel for different aspects of the modeling and we highlight PVDI’s ability to take the best of both worlds. Furthermore, by enriching the process modeling environment with graphical elements, the complications of temporal logic are hidden from the user. To show the practical viability of PVDI, we present tooling supporting the full PVDI lifecycle and test its feasibility in the form of a performance evaluation. ∗H. Groefsema, P. Bulanov, and M. Aiello are with the The Johann Bernoulli instituut for Mathematics and Computer Science, University of Groningen, Nijenborgh 9, 9747 AG Groningen.