Data, Conceptual and Variant entities may have elements.
Conceptual entities do not get transformed into database files in the repository, and so cannot have identifying elements.
Variant entities can only inherit their identifying element(s) from another entity as the result of a Variation relationship.
External entities are defined in the repository and cannot have their elements maintained in any way.
If an element is not part of an entity, it is an unattached element.
Abstractions are not entities and may not contain elements.