Software requirements change taxonomy: Evaluation by case study

Although a number of requirements change classifications have been proposed in the literature, there is no empirical assessment of their practical value in terms of their capacity to inform change monitoring and management. This paper describes an investigation of the informative efficacy of a taxonomy of requirements change sources which distinguishes between changes arising from 'market', 'organisation', 'project vision', 'specification' and 'solution'. This investigation was effected through a case study where change data was recorded over a 16 month period covering the development lifecycle of a government sector software application. While insufficiency of data precluded an investigation of changes arising due to the change source of 'market', for the remainder of the change sources, results indicate a significant difference in cost, value to the customer and management considerations. Findings show that higher cost and value changes arose more often from 'organisation' and 'vision' sources; these changes also generally involved the co-operation of more stakeholder groups and were considered to be less controllable than changes arising from the 'specification' or 'solution' sources. Overall, the results suggest that monitoring and measuring change using this classification is a practical means to support change management, understanding and risk visibility.