it means also that inner object is created and destroyed with parent class, which is enough for stating aggregation. Right ?.
No, it doesn't...
Nesting is about definition and access.
As Geert pointed out, HOW you access the inner class and particularly WHEN you destroy it establishes the
nature of the relationship.
Unfortunately, the general case also applies in the the particular.
There is a REASON why UML says that aggregation (whether shared or composition) is an extension/specialization of the Association relationship. If I create a nested definition and never instantiate the class, do I have a nested class (yes) do I have an aggregation (no)?
The point that Geert and I are still trying to make is that from the framework code
only you CAN'T determine whether the Association (Attribute) is an aggregate or not (for reverse engineering). You have to supply more information.
Anyway, I think we may have to agree to disagree.
HTH,
Paolo