As we discussed in the Introduction, use cases are a simple and powerful way to express the functional requirements, or behaviors, of a system. The following chapters describe the basic concepts behind use cases, their basic structure and format, and their contents. We conclude with a description of an excellent way to get started with use-case modeling: with a workshop.

The intent of these chapters is to gradually introduce you to the basic concepts by successively revealing more detail—much in the way that one peels an onion. The earlier chapters provide basic but important information upon which the later chapters build. As a result, nearly everyone who works with use cases in even a casual way will find the first few chapters useful, while those who write use cases will want to read Chapters 1–5 in their entirety.

The goal of Part I is to allow you to identify actors and use cases, give them brief descriptions, and to start outlining and describing the use cases. Part II provides more information on how to deal with the practicalities of writing use-case descriptions, structuring the use-case model, managing details in the use-case descriptions, and handling the daily complexities of working with use cases.

So without further preamble, let’s get started.