*Container1 logically contains structural element1 if and only if
that container1 logically contains that structural element1 at some position
or logically contains some structural element2 at some position
where that structural element2 is some container2 that logically contains that structural element1.
PermanentFact = False
HiddenFact = False
InternalUniquenessConstraint1
InternalUniquenessConstraint
It is possible that some container logically contains more than one structural element
and that some structural element logically belongs to more than one container.
In each population of container logically contains structural element, each container, structural element combination occurs at most once.