Functional requirements of a models
A function model or functional model in systems engineering and software engineering is a representation of the functions (activities, processes, operations) in the system or model area.
Example of a function model of the "Repairable spare parts maintenance" process in IDEF0 notation.
A similar function model with the activity model or process model is a graphic representation of a company within a defined scope. The benefits of the function model are used to describe the functions and processes, help with the discovery of information needs, help identify opportunities, establish a basis for determining the product and service expenses