*Date:* AUG 1992

(synonym): constraint

(sense-of): system

(refer-to): Mesarovic, Ashby, Rosen

**Synopsis: **A constraint. A constraint can als bo understood as a constraint of some variety. In classical systems theory (Mesarovic), a system is a sub-set of a relation, the constraint being the difference between the cartesian product (the full variety) and the system. Each dimension of the cartesian product is seen as an element of the system. On a constructivist view (Ashby, Rosen) the constraint is constructed by the negative action of an observer. The constructed "frame"delineates the boundaries of the system.