Summary

We began this chapter with a discussion of what requirements are and just how important it is in real life, not just system development, to create and understand your requirements. You learned the unfortunate consequences (both personal and project-related) of not attending to requirements first. We also noted the various types of requirements.

From there, we moved on to discuss how to model requirements using UML. We revisited use cases, and you learned the key characteristics your use cases must have in order to be created properly. We also revisited actors and talked about generalizing their roles. We briefly mentioned some unusual actors such as time and earthquakes and how to use such events as actors.

We also covered new ground on the relationships that can exist between use cases. There, you learned the key differences between the include and extend relationships and how they alter the flow of use cases. You were also warned of the various pitfalls of these relationships. We provided a template and guidance on how to create good use case specifications.

Lastly, we reviewed sequence diagrams, and you saw how they provide a different and important view of use case scenarios that complements the textual use case specifications. We also introduced some new UML elements that you might encounter in sequence diagrams.