Imposing MetaAssociation Uniqueness
This prevents connecting several objects to the same object.
Example: To ensure that an org-unit is connected to a single tag, you must specify on the MetaAssociationEnd between Org-Unit and Tag that the MetaMultiplicity attribute is 0..1 or 1.
Uniqueness is applied particularly on sub-type and certain composition links.
+ For compatibility with versions earlier than Service Pack 1 of HOPEX version 6.1, it is also possible to specify the _CardMax attribute between MetaClass and MetaAssociationEnd. This characteristic takes value "U" to impose uniqueness . Other possible values for this characteristic are "1", which means that the uniqueness is only for documentary purposes, and "N", which indicates there is no restriction.
Only the maximum MetaMultiplicity is taken into account to impose uniqueness of a MetaAssociation. The minimum MetaMultiplicity of a MetaAssociationEnd is purely for documentary purposes. It does not give an obligatory MetaAssociation.