Executable UML: A Foundation for Model-Driven Architecture

13.5. Reclassification

In the bookstore, the warehouse makes a policy of hiring clerks who can take on several roles, so that the shipping clerk is really just one kind of a more general warehouse clerk. Sometimes a warehouse clerk may be processing shipments, at other times the same clerk may be assigned to restock product, and at still other times the clerk may be off duty.

Because a single clerk can take on several roles during a shift, there must be a mechanism to support reclassification, in which an instance of one subclass becomes an instance of a different subclass in the same hierarchy.

Executable UML recognizes the need for reclassification in the context of a generalization and specialization hierarchy when an object playing one role ...