Gladys Kaplan

Enhancing a requirements baseline with scenarios

Scenarios are well recognised as an important strategy towards understanding the interface between the environment and the system as well as a means of eliciting and specifying software behaviour. We adopt a broader view of scenarios. For us, a scenario is an evolving description of situations in the environment. Our proposal is framed by Leite’s work on a client-oriented requirements baseline, which aims to model the external requirements of a software system and its evolution. Scenarios start by describing the environment situations, according to the main actions performed outside the software system. Scenarios also help to clarify the interrelation between functional and non-functional requirements. We have validated our strategy and the related representations based on case studies.

A Scenario Construction Process

Scenario is a description technique that has been attracting a lot of attention from practitioners and from researchers. Several disciplines have been using scenarios for some time now, but recently the information system community has dedicated special attention to the possibilities that this description technique provides to enhance understandability of task-related descriptions and communicability among stakeholders. This paper aims its attention at a particular scenario construction process, but while doing so it tackles important problems regarding scenario management, in particular scenario organisation. Our scenarios are described in a structured way, using a simple conceptual model together with a form-oriented language. We have been using this representation for some time now, and our results are based on several case studies conducted with real-world problems.

Defining System Context Using Scenarios

It is already well known that in order to define the software system requirements deep knowledge of the universe of discourse is needed. This includes not only what is actually happening but also what the plans for the future are. Unless the requirements engineer has a previous knowledge of the domain, he or she may become overloaded by data of different nature. To cope with this, a gradual process which slowly migrates from learning to definition is advisable. During the learning phase, the focus should be placed on the current facts which should be organized and recorded. Later, the forthcoming plans should be also understood but instead of recording them as they are, they should be used to design future universe of discourse models. This chapter focuses on the description of current situations and lays foundations for the description of future situations by means of an evolution process.