5.2 Entities and Elements

An Entity's type directly influences its elements. The entity type will determine the other entity types to which it can be related and whether an identifying element can be specified.

Because the entity type determines how an entity is implemented in the repository, rules must apply to what an entity contains:

• Conceptual entities cannot be assigned identifying elements (remember, conceptual entities are not implemented as files).

• Variant entities cannot be assigned an identifying element. It receives an identifying element as the result of a Variation relationship from a Data or External Entity.

• External entities cannot have their elements maintained (remember, the underlying physical or logical file definition is not modified by the modeler).