Requirements Engineering Decisions in the Context of an Existing Architecture: A Case Study of a Prototypical Project

The role of an existing systems architecture (SA) in requirements engineering (RE) is recognised as important, but under-researched. A recent exploratory study of ours investigated this issue in a laboratory setting involving student participants. While the initial findings are promising, much work still remains to solidify the results. Therefore, we conducted a replication of the study, and its significant extension, on a large-scale prototypical rail project. Specifically, we identify (i) the effects of SA on RE decisions, (ii) the characteristics of the RE decisions and (iii), the impact of such decisions on development activities and the rail system. The findings of this study have implications on tighter RE-SA integration across subsystems, impact analysis of requirements on SA, and planning and risk management. We also propose three emergent hypotheses from this case study as a driver for future empirical work in RE. This case study involved examining the 10-year history of requirements and architecting decisions in several major components of the rail project. The data collected was from numerous project documents and extensive interviews with the developers and planners.