The nonfunctional requirements describe the qualitative behavior, or the "how well" qualities, of the productwhether it has to be fast, or safe, or attractive, and so on. These qualities come about because of the functions that the product is required to carry out. Even something as simple as the common household tap shown in Figure 8.7 has nonfunctional requirements that make the difference between success and failure:
Figure 8.7.How many nonfunctional requirements does a common household tap have?
At this stage you have written a description and usually a rationale that captures the intention of the nonfunctional requirements. Some of them may seem a little vague, and some of them may appear to be well intentioned and little more. Please keep in mind that you have not finished with these requirements, because you have yet to write the fit criteria. When you do so, you will write a measurement to quantify the meaning of each requirement. We look at this task in the next chapter. |