To respond in part to Pete Wilson's email: addressing the question "... why you want both a work AAP and an expression AAP in your bib record", I am attempting to follow these RDA instructions:
5.5 Authorized Access Points Representing Works and Expressions
Construct the authorized access point representing the work ... 6.2.2
When constructing an authorized access point to represent a particular expression of a work ... 6.27.3
18.104.22.168 For an original work or a new work based on a previously existing work, construct the authorized access point representing the work ...
22.214.171.124 Construct an access point representing a particular expression of a work ...
And in so doing, to fit them into the MARC format as best possible. My understanding is, as Pete says "If there is only one such expression, we currently put the title part of its AAP in a 240, assuming the title proper won’t do double
duty." That's how catalogers are using the MARC format, when using field 240.
Supposing someone said (not me!): "You can have a 240 field for the work or a 240 field for the expression, but not both." Would that statement be correct? RDA, the sections I quote above, seems to instruct to provide both.
Responding to Kevin Randall's suggestion "... have the MARC record be a description of the manifestation, without any 'main entry' at the top": If I understand correctly, this would effectively do away with field 1XX. It's a logical consequence of the line of thought. But before we go that far, please remember the books, which are put on shelves in order within a class, by cutter number, which is based on main entry.
Sincerely - Ian
Cataloging and Metadata Services Librarian
George Mason University