Requirements analysis for large scale systems

All readers of this paper most likely have knowledge of the software requirements discipline and of the use case notation, however not everyone is aware that with the progress of the development process, requirement models evolve in different ways. In particular, some artefacts (such as the glossary, for example) are simply enhanced, while others (functional requirements, object model, etc), in different stages of the process encapsulate different aspects of the system and satisfy different needs. Therefore, while the former require one to maintain only the most updated version, the latter require the maintenance of different versions (e.g. business functional requirements, domain functional requirements, etc). As expected, this is more evident in the context of large scale systems. Furthermore, a review of IT literature brings to light some inconsistency in the use of use case notation and, more generally, in requirement models and, even more importantly, to the lack of guidelines related to how to successfully address the requirements analysis for large scale systems. The objectives of this paper are to clarify the terminology of software requirement models by suggesting a more consistent usage, to describe the different versions of requirement models, and to illustrate how to effectively address requirements analysis for large scale systems. This paper is supported by a real case study related to a large scale project implemented in a tier 1 financial organisation