Performance criteria Functional requirements are the same as objective wishes. Functional requirements are those necessary, life-sustaining demands that we place on our environment. The requirements for fire worthiness are covered by the building code. 15 Formulation of functional requirements Functional requirements should be formulated in detail. Usually they are expressed in words, but it is possible to tie them directly to measurable quantities.
Functional requirements are relatively independent of the various external conditions.
In the planning task, there will always be conditions that have an influence on the finished solution independent of the functional requirements. These are called given conditions. Some of these conditions can be used, but most are limiting and will make an optimum solution difficult. In rare cases it is possible to satisfy all functional requirements. Even so, the given conditions will force compromises and partial solutions.