constraint

A restriction that determines which days and times an activity may be scheduled at, or which resources may be allocated to the activity. During scheduling, constraints on different items can determine the day and time of the activity. For example, an activity's required location might be available only on Mondays and Wednesdays, but a maximum hours constraint on the required staff member might mean that they cannot be allocated to any more activities on Mondays. See hard constraint and soft constraint.