1. Expressing functions

The functions of a solution are the expected performance and the constraints it must meet. Numerous ways of expressing the functions of the solution under study have been developed, with varying degrees of sophistication:

• ask users to answer the question "What's it for?

• analyze documents and sales pitches ;

• observe usage processes, by various users, and describe "what the object does";

• collect dissatisfaction through a quality organization or after-sales service;

• transform technical specifications into functional specifications.

You can then carry out a systematic and exhaustive exploration of functions by conducting a lifecycle analysis of the solution under study:...