UML25 — how to instantiate associations between stereotypes

UML says: ” Stereotypes can participate in binary associations. The opposite class can be another stereotype, a non-stereotype class that is owned by a profile, or a metaclass of the reference metamodel.”

How are instances of these stereotypes and associations to be serialized?

For example, look at SysML1.3 in which the stereotype ValueType has an association named A_valueType_unit to the stereotype Unit.

How is a SysML 1.3 model supposed to instantiate this? There will be an element representing the stereotype instance of this form:

<sysml:ValueType xmi:id="id1" base_DataType="id2" unit="id3"/>

What should id3 be the identity of? Presumably the target stereotype instance? Or the model element to which the target stereotype instance is applied?

Is such an association allowed to be a composition? If so what would be the deletion semantics?

Also, would we really expect to see any elements of this form?

<sysml: A_valueType_unit xmi:id="id4" valueType="id1" unit="id5"/>?

The following sentence: “For these associations there must be a property owned by the Stereotype to navigate to the opposite class. Where the opposite class is not a stereotype, the opposite property must be owned by the Association itself rather than the other class/metaclass” appears to imply that we would never see such an element, but I don’t know of any statement to confirm this

Clarify non-trivial aspects of associations defined in the context of a profile:
• Serializing instances of associations is optional for XMI.
• Associations can be composite or not.
• Clarify the kinds of Types allowed to be defined or imported in a Profile.
• Instances of stereotypes are owned by the link instance of the composite association corresponding to
the mapping of the stereotype extension.
• Fix the incorrect reference to section 14.3 of the MOF Core spec to 14.4 instead.
Note that clause 12 lacks a notation for instances of Profile-defined Classes, DataTypes and Associations.
Specifying such notation is a separate issue.