  We consider requirements for cyber-physical systems represented in
constrained natural language. We present novel automated techniques for aiding
in the development of these requirements so that they are consistent and can
withstand perceived failures. We show how cyber-physical systems' requirements
can be modeled using the event calculus (EC), a formalism used in AI for
representing actions and change. We also show how answer set programming (ASP)
and its query-driven implementation s(CASP) can be used to directly realize the
event calculus model of the requirements. This event calculus model can be used
to automatically validate the requirements. Since ASP is an expressive
knowledge representation language, it can also be used to represent contextual
knowledge about cyber-physical systems, which, in turn, can be used to find
gaps in their requirements specifications. We illustrate our approach through
an altitude alerting system from the avionics domain.
