I don't know much about MARC. I do know that I tried to put together a
3NF ERD for the stuff I wanted to do with my personal library, and
ended up with a thing with a couple of dozen different tables, and
realized that the MARC format (which I'd seen at a previous library)
makes things considerably easier.
Basically, a MARC record has a bunch of fields; each field has a type.
You can have a bunch of fields of the same type in the same record; you
don't need to have fields of any particular type in any record.
This simplifies representing things like books, where you usually have
zero or more authors, zero or more subjects, zero or more copies, etc.
But this is all guesswork -- don't trust it! Let me know if you learn
-- <firstname.lastname@example.org> Kragen Sitaker <http://www.pobox.com/~kragen/> Computers are the tools of the devil. It is as simple as that. There is no monotheism strong enough that it cannot be shaken by Unix or any Microsoft product. The devil is real. He lives inside C programs. -- email@example.com