Associations and Roles in Object-Oriented Modeling

We present an extended ER model with entity, role, and association as the basic constructs for object-oriented modeling. The purpose of the constructs is to support object evolution and extension for long lived objects. A class hierarchy consists of a static part and a dynamic part. The static part is a classiication of entity classes, while the dynamic part is the role classes played by entities. The interaction among objects are captured with association classes. Based on the observation that entities play roles in association with other entities, we provide a uniied view on roles in associations and roles as an extension to objects. The proposed modeling constructs help developers better understand the interrelationship among entities, thus result in exible implementations for dynamic systems.