In software engineering, such an abstract descriptive model is called Entity–Relationship model (ER model) and describes the entities (=UBIK® metaclasses) and relationships between them. Usually this information is depicted in an entitiy-relationship-diagram (ERD), which draws the corresponding data objects and relations as rectangles and lines between them, respectively.
[[File:UDOM_Relating4.png|thumb|600 px|alt=ER-model|Entitiy-Relationship-Model]]
The metaclass „CONTROL“ can be drawn as diamond, signalling the additional block between these two metaclasses, which is always needed for each relation of cardinality n : n.
===About References and Relations===