definition a constraint which must hold before an activity can
take place
variants An input can be one of several types. We have
identified four types: authority, condition, resource and other. "Other''
is provided to allow for enhancement to the model, for instance to the
addition of spatial constraints.
examples see authority, condition and resource
term in other fields In IDEF, there are three inputs to an
activity: input, corresponding to our condition;
control, corresponding to our authority; and mechanism,
corresponding to our resource.