Definition of the term („What is a functional specification?“)
A functional specification contains a contractor’s detailed description how he intends to solve the customers requirements. As the preceding instance, however, the contracting entity must define the user requirement specification as detailed as possible in a functional specification. This way, it is advisable that the contracting entity first accepts the functional specification before the contractor begins with the implementation.
Furthermore, it is common practice to apply the inclusion and exclusion principle when creating a requirement specification to explicitly ignore or include specific cases. With reference to software development, the functional specification is also defined as part of the V model.