Abstract: A computer aided system design tool which enables the user to define the system functionally by defining functional program requirements (28) and defining preliminary system requirements (30). After the program requirements (28) and preliminary system requirements (30) have been defined, an automated reuse tool (38) selects particular implementations for each of the functions specified by the user when defining the functional program requirements (28). The automated reuse tool (38) also partitions the system constrains defined by the preliminary system requirements (30) over the system by proper selection of particular implementations for each design. The resulting reuse design database (40) may then be simulated (42) to verify proper operation of the system.