Behavior Consistent Extension of Object Life Cycles

Various notions of conformance between operations of a subtype and operations of a supertype have been proposed (e.g., contravariance and covariance). Similarly, different notions of "consistent extension" of object life cycles can be defined to meet various objectives.

This paper treats inheritance of object life cycles in the realm of behavior diagrams that identify legal sequences of states and activities (operations). It presents necessary and sufficient rules for checking three different kinds of conformance (observation consistency, weak invocation consistency, and strong invocation consistency) between a behavior diagram of a subtype and that of its supertype.