Constraint management plyas an important role in design applications where constraints reflect design restrictions and design decisions. ECA rules are a widely used mechanism to enforce constraints. The paper argues that such rules must be augmented for design environments by a spatial and a temporal dimension of validity, resulting in so-called area-event-condition-action (AECA) rules. The spatial dimension allows to restrict constraints locally in the design space, and to control interaction between designers. The temporal dimension permits designers to retract their designs to earlier stages. The paper introduces the concept of AECA rules, motivates them by examples from building design. discusses rule, motivates them by examples from building design, discusses rule management, and then introduces two important issues, conflict detection during collaboration, and backtracking during design revision.