Applied Software Project Management

Chapter 6. Software Requirements

It seems obvious that we need to know what software is supposed to do before we build it. Nevertheless, many projects are delayed (or fail completely) because development begins before anyone on the project team really understands how the software should behave. The solution to this problem is to take the time to gather and verify the software requirements— documentation that completely describes the behavior that is required of the software—before the software is designed, built, and tested.

When starting a new project, programmers are often tempted to just dive in, beginning to build the software as soon as they have the general gist of what it is supposed to do. It's not hard to see why people do this: many programmers develop advanced programming skills without ever having to figure out and write down the requirements for even a simple software project. For example, many good programmers hone their craft by building software that they intend to use themselves. In these projects, the programmer does not need to take time to understand the behavior of the software—she intuitively knows what the software is supposed to do from the beginning of the project.

However, most software is built to meet the needs of someone other than the programmer. If those needs are going to be satisfied, the behavior of the software must be planned before the software is built. Software requirements engineering is the art and science of developing an accurate and complete ...