It would be useful to write one description of software behavior to serve both requirements and design. Having one
description could reduce effort by eliminating the work of
developing two descriptions and of keeping them consistent
and relevant throughout development, evolution, and sustainment.
It would also eliminate the inconsistency inherent in
having two descriptions, a fertile source of error. A question
paramount to software engineers is, Could one description of
behavior for a real system serve both requirements and
design? This paper answers that question by describing one
such description of the software behavior of a real system.