Software Requirements ”Background
Software tools are developed for different reasons. For example, some people write software for their enjoyment; others write software to fulfill course requirements; yet others develop software systems to solve a problem they face. This chapter examines software systems that are developed for real customers in order to fulfill a customer s need. Relevant questions that should be asked at this stage are: How do customers define their needs? How can software developers help customers define the requirements?
In Chapter 2, we discussed how different software development methods deal with customer requirements. For example, the Unified Process describes use cases, which are what the user wants a computer system to do. The use cases usually represent the highest risks, and the requirements can be derived from them. Another approach to requirements definition is presented by eXtreme Programming (XP). XP advocates that in order to produce the software the customer needs, the customer should be on-site to give the developers ongoing feedback. In addition, XP outlines a very specific process (the Planning Game) for defining customer requirements (called customer stories ).
As hinted before, the specific development method one uses is of less importance as long as it ensures that customers get what they need. From this perspective, in the continuation of this chapter we look at how software requirements may be gathered.
This discussion is based on the requirements lists created in Task 1. During this discussion, each list can be checked, for example, according to its completeness and consistency. After several lists are reviewed, we recommend checking whether one system ”that is, one characterized by combining several requirements lists ”can be developed. In this way, we may get one product and the company may become a product-based company (in contrast to a company that has several versions of the same product, each version tailored for a specific customer).
If, during that discussion, requirements are changed, updated, altered , and so forth, discuss the reasons that lead to these changes. This is, in fact, how the process of defining requirements happens in everyday life and it is an excellent opportunity to reflect on that process (see Chapter 10, Learning Processes in Software Engineering ).