Gene Fieg sent some interesting mail to the RDA-L mailing list on Monday. Look through the responses for good comments.
After reading RDA and its application of FRBR, it seems that we dealing with librarianship’s application of Platonism, especially in the descriptions work, expression, manifestation, and item. There really is no “work”; it is like a Platonic form, which is reflected in its physicality by expression, manifestation, and item. We, as catalogers, actually deal with the item. So perhaps in the real world the relationship should be item, manifestation, expression, work. The item points to the manifestation which points to the expression which points to the Platonic ideal, work.