SEM Functional Design Stage

The functional design process maps the "what to do" of the Requirements Specification into the "how to do it" of the design specifications.  During this stage, the overall structure of the product is defined from a functional viewpoint. The functional design describes the logical system flow, data organization, system inputs and outputs, processing rules, and operational characteristics of the product from the user's point of view.  The functional design is not concerned with the software or hardware that will support the operation of the product or the physical organization of the data or the programs that will accept the input data, execute the processing rules, and produce the required output.

The focus is on the functions and structure of the components that comprise the product.  The goal of this stage is to define and document the functions of the product to the extent necessary to obtain the system owner and users understanding and approval and to the level of detail necessary to build the system design.

Prototyping of system functions can be helpful in communicating the design specifications to the system owner and users.  Prototypes can be used to simulate one function, a module, or the entire product.  Prototyping is also useful in the transition from the functional design to the system design.