[Modeling] Modeling an Agent Class- change of classes
Thu, 26 Jun 2003 14:41:14 +0200
> In dynamic classification, an entity can change its class at
> run-time. Say, an object of class A becomes an object of class B.
> That is what I meant by 'change classes'.
OK, I think I see your point. The basic situation is
Person [playingTheRoleOf Employee] isPartOf Company
in a model with two classes (Person and Company) and
an aggregation between them with a role name Employee.
Then, if you destroy a particular company, say Enron, all
aggregation links involving Enron will be deleted. But the
involved persons continue to exist. So in this basic
external model (not adopting the view of any particular
company), there is no Employee class, but only a role
You can reify/"objectify" this aggregation into an association
class isEmployedBy/Employment with suitable attributes. So, we
Person [playingTheRoleOf Employee] isEmployedBy Company
But you cannot use an Employee subclass of Person in such
an external (company-independent) model.
Maybe that's what you wanted to suggest:
Person isSuperClassOf Employee isPartOf Company
But that's not a correct model, because you would need
several Employee instances for the same person (one for
each employment of that person), which is not consistent
with the isSubclassOf relationship.
You could use an Employee subclass of Person (associated
with Company by means of an aggregation) in an internal model
adopting the perspective of a particular company, such as Enron
(this class denotes, in fact, "EnronEmployee"). But then
you would no longe have other (non-Enron) employees in