Specification of software under the box structure method requires a co
mplete, consistent, and traceably-correct description of behavior sole
ly in terms of external stimuli and responses. Such a specification, a
lso called a black box, can be derived from the requirements through s
traightforward, systematic enumeration of all stimulus sequences. Enum
eration is made manageable by the application of techniques for contro
lling the growth of this inherently combinatorial process, and specifi
cations at different levels of abstraction may be combined to refine a
black box specification. This work presents a unifying framework for
development of specifications and testing models, and the focus on req
uirements traceability provides an explicit means to manage requiremen
ts change. (C) 1998 John Wiley & Sons, Ltd.