hey folks-- I have some message properties i'd like to cache in notmuch that strictly apply to specific subparts of the message. (e.g. session keys for an encrypted part, signature verification status of a signed part) let's assume that for any given copy of a message, we have a reliable "address" scheme for a part (e.g. "1.2.1.1"). However, this becomes confusing with multiple copies of a given message. It's possible that one copy of the message has one MIME structure, but mangling (by MTAs, mailing lists, etc) result in a different MIME structure in another copy. For cryptographic properties, it might be nice to associate a subpart with a particular cryptographic digest of the subpart itself. Alternately, from a filesystem perspective, maybe it would be better to label the subpart based on the underlying physical file, and the subpart's "address". Are there other options? If you wanted to associate a message property with a subpart of a given message in a way that was reliable, especially in this new era of multiple copies of a message, how would you do it? --dkg