  In the Ramadge-Wonham supervisory control theory the only interaction
mechanism between supervisor and plant is that the supervisor may
enable/disable events from the plant and the plant makes a final decision about
which of the enabled events is actually taking place. In this paper, the
interaction between supervisor and plant is enriched by allowing the supervisor
to force specific events (called forcible events) that are allowed to preempt
uncontrollable events. A notion of forcible-controllability is defined that
captures the interplay between controllability of a supervisor w.r.t. the
uncontrollable events provided by a plant in the setting with event forcing.
Existence of a maximally permissive, forcibly-controllable, nonblocking
supervisor is shown and an algorithm is provided that computes such a
supervisor. The approach is illustrated by two small case studies.
