  This paper describes a case study conducted in collaboration with Nortel to
demonstrate the feasibility of applying formal modeling techniques to
telecommunication systems. A formal description language, SDL, was chosen by
our qualitative CASE tool evaluation to model a multimedia-messaging system
described by an 80-page natural language specification. Our model was used to
identify errors in the software requirements document and to derive test
suites, shadowing the existing development process and keeping track of a
variety of productivity data.
