DEV475 Mastering Object-Oriented Analysis and Design with UML ...

Module 6 - Use-Case AnalysisThe Role of an Entity ClassThe Role of an Entity ClassActor 1Actor 2Store and manage information in the systemMastering Object Oriented Analysis and Design with UMLCopyright © 2003 Rational Software, all rights reserved 19Entity classes represent stores of information in the system. They are typically used torepresent the key concepts that the system manages. Entity objects (instances of entityclasses) are used to hold and update information about some phenomenon, such asan event, a person, or a real-life object. They are usually persistent, having attributesand relationships needed for a long period, sometimes for the lifetime of the system.The main responsibilities of entity classes are to store and manage information in thesystem.An entity object is usually not specific to one Use-Case Realization and sometimes itis not even specific to the system itself. The values of its attributes and relationshipsare often given by an actor. An entity object may also be needed to help performinternal system tasks. Entity objects can have behavior as complicated as that of otherobject stereotypes. However, unlike other objects, this behavior is strongly related tothe phenomenon the entity object represents. Entity objects are independent of theenvironment (the actors).6 - 19