Working with this right now, in fact. Our solution isn't very METS-y,
so ditto on the queasiness....
We have a METS for each of our digital library images--sim. to your
"small METS". These are aggregated by "big METS" that represent
physical objects like books, etc. Like you, we need our references to
be reciprocal. For every METS we have, there is a mets:dmdSec[@ID =
'pulContextMD'] that looks like this:
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dcterms="http://purl.org/dc/terms/">
<rdf:Description rdf:about="http://diglib.princeton.edu/assets/pudl0017/wc064/H/0001/00000001/"> <!-- this is me -->
<dcterms:isPartOf rdf:resource="http://diglib.princeton.edu/objects/pudl0017/wc064/H/0001/"/> <!-- I'm a part of... -->
Not really descriptive metadata, other than the dcterms:title but....
Everything here could be mapped to the mets root or header, except for
the the dcterms:isPartOf element, which points to the host object (the
rdf:Description/@rdf:about), thus fulfilling the need you're
describing. What's especially nice is that that property can be
repeated, which means that anything can be 'part of' anything else, and
that every METS knows both its ancestor(s) and its descendant(s).
C-17-D2 Firestone Library
Princeton, NJ 08544
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