Design specifications

Design specifications are detailed descriptions of functionality, behaviour and look & feel guiding the realisation of a product, service or application.

A design specification document outlines the implementation: how something is supposed to be done.

“Specifications may take several forms. They can be a straightforward listing of functional attributes, they can be diagrams or schematics of functional relationships or flow logic, or they can occupy some middle ground. Specifications can also be in the form of prototypes, mock-ups, and models.”

(Excerpted from philosophe.com)