A constraint is an implementation of an explicit rule ( examples).
Often, the trigger for the system malfunction is a normal event, arriving when the system is in an exceptional situations. The normal event may transit the system to an unexpected state ( Perrow, 1984 ). Therefore, the constraints should depend on the situation, namely they should be scenario-based.
A rule may be implemented either locally or systematically.
Updated on 29 Mar 2016.