An EER object is called an entity and EER object classes are called entity-sets. The EER model supports simple, primitive or abstract attributes; class hierarchies; and controlled classes of enumerated atomic values or ranges of values. In EER, abstract attributes are specified as relationship-sets between (and external to) entity-sets, rather than local to entity-sets. The EER model does not support set-valued attributes, tuple attributes, union value classes, and derived classes and attributes. However, set-valued attributes can be modeled using additional (auxiliary) entity-sets, tuple attributes can be specified using auxiliary relationship-sets, and a union value class can be specified using an auxiliary entity-set specified as a generalization of the entity-sets that are involved in a union value class.