The purpose of the personal file number is to make a document easier to find, in other words, you know that document M0034 is right after M0035. If you give a document two different file numbers, then you will have to make two copies and store them in two different places, since obviously one physical document can't be in two places at the same time. As the Clooz manual says, DO NOT file documents by surname, because then you have to have DUPLICATES (exact wording and obnoxious capitals mine). So, if you are looking for the right answer in Clooz philosophy terms, you should give a document one id, and then link the various people to it.