As far as I understand the IMS repository, the question
item used as above, first in a formative test at the
end of a chapter, and then in a summative test at
the end of the term, would be such an example, and a
third usage might occur if the question item is only
conditionally accessed if the student's age is > 90
(well, perhaps the question is asked in a neurology
department, after all).
If the items are in the same repository and on the same
level as webcontent items used for chapter content,
this would IMO simplify at least the user interface,
and I would guess that also the actual coding could
be simplified if a clean simple division of labor and
simple concepts of "item" are applied.