A scenario is a specific instance (typically classified as
normal or alternative scenarios) providing a high-level visual representation
of user requirements and logical scenarios. Basic use-case
notation illustrates actors as stick figures, use cases as ovals, and
the system boundary as a box border. Use case diagrams are
relatively simple, but are supported by extensive written descriptions
of system behaviour (preconditions, post-conditions, normal
and alternative course, exceptions and business rules). Activity