Concurrent computations and VLSI circuits

VLSI is a medium in which computations can be realized that exhibit a high degree of concurrency. Concurrent computations require a very careful design technique, for, as we know, uncontrolled concurrency results in uncontrollable complexity. This observation makes complexity control a conditio sine qua non for VLSI design. We know of only one effective technique of complexity control: modular design. Using this technique, the design of a component amounts to the choice of subcomponents and relations. The relations express how the parts (the subcomponents) constitute the whole. Designing the subcomponents in a similar fashion, we obtain hierarchical components. Given the specifications of the subcomponents and the way in which the subcomponents constitute the component, we must be able to show that the whole component meets its specification. The specifications should not reflect the internal structures of the components: they must specify their net effects only.