ABSTRACT
The system functional requirements specify the high-level design of the system that we develop to implement the operational model. In the functional requirements, we design a new abstract machine onto which we map the behavior of the abstract machine we created for the user in the operational specification. This new abstract machine ultimately maps onto a particular programming language model that, in turn, will map onto a real computer system. At the functional level, we tackle the problem of
how
each of the operations is performed. The end user neither sees this machine nor does he have any need to know about its operation.
