Jun,
Good questions. There are definitely instances in which a user belongs to more than constituency simultaneously (e.g. faculty, staff). It can also be argued that students are simultaneously students and alumni. It would be nice if there were a way to accomodate that. But I think for purposes of simplification we can live with one extended profile per user corresponding to their primary constituency. When a status changes (e.g. student graduates and becomes an alum), then we would have some procedure to move relevant overlapping attributes.
