It Will Never Work in Theory

Software Requirements Change Taxonomy: Evaluation by Case Study

Posted Oct 28, 2011 by Neil Ernst

| Organizational Studies | Qualitative Studies |

Sharon McGee and Des Greer, "Software Requirements Change Taxonomy: Evaluation by Case Study", International Conference on Requirements Engineering, Trento, Italy, September 2011.

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.

Many people have considered how best to classify requirements changes: for example, Harker (pdf) or Zowghi (pdf). In this paper, the authors conducted a single case study to understand whether their taxonomy could not only capture the various changes which occurred during an industrial software development project, but also whether such a classification could help with project management concerns.

It is a well-worn truth that changes in requirements can be very expensive to fix later in the project. However, one of the things that is typically not considered is the opportunity that a change affords. We tend to focus on the negative, but as McGee demonstrates during her case study, these changes are a key part of business strategy.

In particular, the highest-value/highest-cost changes came from the strategic, organization level, and the lowest-value/lowest-cost changes to the system from the detail-oriented, solution implementation level. The classification of change origins provides evidence that the context of the change is important in understanding how to manage that change.

During her research presentation, Sharon McGee also commented on the challenges of this type of research. While valuable, the organization she embedded with found the research process time-consuming. She doubted they would be willing to undergo a follow-up study. This is a major barrier to obtaining case study opportunities that go beyond the anecdotal.

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