Formalizing the transition from requirements’ change to design change using an evolutionary traceability model

Abstract

The ideal outcome when responding to changes in the functional requirements of a system is that we can quickly determine (1) where to make the change, (2) how the change affects the architecture of the existing system, (3) which components of the system are affected by the change, and (4) what behavioral changes will need to be made to the components (and their interfaces) that are affected by the change of requirements. If these facts are known, the impact of the change is entirely understood and therefore manageable. Moreover, a system is likely to undergo multiple changes over the course of its service life, so there is also a need to make a comprehensive record of these changes thus preserving the integrity of the system and potentially extending its service life. To this worthy end, a traceability model using Behavior Trees as a formal notation to represent functional requirements is proposed. This will address the issues cited above, revealing change impacts on different types of design constructs (documents) caused by the changes to the requirements. The proposed model introduces the concept of evolutionary design documents that record the change history of the designs. From these documents, any version of a design document as well as the difference between any two versions can be reviewed, thus affording the desirable condition of full traceability. An important advantage of this model is that the major part of the procedure to generate these evolutionary design documents can be supported by automated tools making the method accessible for use in large-scale software and systems development projects.