Tropes, an object-based knowledge representation system, has been added three important intertwined features: constraints, composite objects and tasks. Constraints provide a declarative means to de ne and maintain relations between objects. The part-whole relation pro ts by constraints for sharing attribute values between a composite object and its components. The task model bene ts from composite objects for task modeling and from classi cation and instantiation mechanisms for task execution; it also uses constraints to propagate input and output data from one task to another.