This attribute gives the number of active pointers associated
with an ObjectObject. It is modified whenever pointers are created or
annulled (by astCloneastClone, astAnnulastAnnul or astEndastEnd for example). The count
includes the initial pointer issued when the Object was created.
If the reference count for an Object falls to zero as the result
of annulling a pointer to it, then the Object will be deleted.