ABSTRACT

The input/output requirement determines the set of all system models, called functional system designs, that satisfy the input/output requirement. System models in this set are compared with respect to the cost requirement. The input/output requirement must specify the required operational life for the system to be designed. A class of input/output requirements very useful for practical, theoretical, and pedagogical purposes are those generated by a set of systems. These are called normal input/output requirements. An input/output requirement is not a system; systems and input/output requirements have essential similarities and differences. The input/output requirement IOR is intended to specify the range of possible (or permissible) behavior for the system to be designed from the external, input/output, technology-free point of view independent of what may be going on inside the system. A system that satisfies the input/output requirement is not, in general, a model from which a real system can be built directly.