No comments on this I guess. I have come around to agreeing that
<citationInfo> works for this element. I don't have a strong opinion
between this and <partDesc>, except that we do want to think of this as
broader than just for document/texts. In BibX, for example, there are
the following "type" options: number, volume, issue, page, chapter,
part, section, paragraph, line, word, track, other. From recent
discussions, it seems like we need quite a bit more, for legal
citations for example.
Anyway, here is an example of the partdesc element in BibX:
I'd venture to say this mix of single and composite items might be
important for some sorts of citations.