XMI24 — XMI composite opposite constraint overly restrictive

Section 9.4.1 of the specification contains the following constraint:

For Properties with isComposite=true, the opposite property is not serialized.

While this is fine when objects are nested it doesn't make sense when an object is serialised as a root object. For example, stereotype extensions are mapped to composite associations. Stereotypes instances are serialised as root objects because the composite property is not owned by the extended class. To attach them to their extended object the 'base' property is serialised, but this is the opposite of a property with isComposite=true.

The constraint should be made specific to where the composite property is itself the
one used for nesting