Behavioural concern modelling for software change tasks

Many modification tasks on an existing software system result in changes to code that crosscuts the system´s structure. Making these changes is difficult because a developer must understand large parts of the system, and must reason about how the modification will interact with the existing behaviour. Typically, developers make these kinds of changes using an ad-hoc approach with tools that help in gaining some understanding of the existing system, but that do not provide any specific support for reasoning about, implementing, or analyzing just that part of the system related to the modification. We present the behavioural concern modelling (BCM) approach and tool that provide direct support for a systematic approach to modification tasks. This approach enables a developer to create a partial, abstract, grounded behavioural model of a concern(s). By grounded, we mean that the relationship between the model and the code is explicit: A developer describes which code contributes to which parts of the model. The examples we describe use a finite state machine as a model. We show how the approach can help a developer capture a concern, reason about design options, and implement modifications.