Role representation in the E-R data model

The authors present a taxonomy of the different types of roles which occur in enterprise domains, and which can be effectively represented using the E-R (entity-relationship) diagram. This is done with respect to roles on attributes, roles on relationship sets, and roles in abstraction hierarchies. Rules for role placement are presented, such that the scenarios for defining roles can be defined in a nonsubjective manner, which is necessary for this activity to be performed by computer. The rules presented constitute a subset of the rules which exist to deal with role placement. In addition, the authors examine role representation from the standpoint of using the generalization abstraction mechanism to reduce complexity and eliminate ambiguity in the modeling of domain situations. The presentation of roles in the E-R model in this manner has proven to be effective in managing the complexity and eliminating the ambiguity that is generally inherent in the real world being modeled