This article is devoted to formation of a subject of engineering decision in intelligent system of development of production processes based on description of functional models of engineering capabilities upon decision making. A subject of design engineering decision is a complicated system including subsystems of various essence, which operate according to rules described by fizzy logics and study cases. Design engineering decision is formed as a consequence of combined operation of intelligent system modules: equipment selection module, tool selection module, and accessory selection module. Each module of design engineering decision is characterized by its unique properties of engineering design both at input and output of decision formation. Therefore, each module of intelligent system of development of production processes is considered as a complex system with inherent properties. The components of a given specific system, for instance, selection of metal cutting equipment, will be input parameters for specific system module. Output parameters of the system of selection of metal cutting equipment will be input parameters for the system of selection of cutting tools, etc.