There are a few problems with section 18.104.22.168 and the content models of associated elements:
1) Not much guidance is given on when to put <biblScope> in which parent element.
2) When guidance is given, it's for journal articles (to put volume and issue number in <biblScope>s <imprint>), but the information there doesn't "relat[e] to the publication or distribution of a bibliographic item", as <imprint> is currently defined.
To address (1), we propose to explain more explicitly in the Guidelines that <biblScope> be used to constrain the scope (within the parent element of the biblScope) of the item cited in the next lowermost "level", where "level" is used as in section 22.214.171.124. Take this example:
<title>Herakles to Poseidon</title>
<title>Cults of Boiotia</title>
<title>Bulletin of the Institute of Classical Studies
There are four "levels": the lowest "level" is the <analytic>, the next is the first <monogr>, then the second <monogr>, and finally the highest "level" is <series>. The article "Iolaos" appears on pp. 64-70 of *Herakles to Poseidon*, which is part 2 of *Cults of Boiotia*, which is vol. 38 of *BICS Supplements*.
Each <biblScope> describes where (within its parent element) to find the thing in the previous level.
To address (2), we would remove the current recommendation in 126.96.36.199 to use monogr/imprint/biblScope for journal articles and instead say to encode information like volume, issue, and date of a given journal issue as a child of <monogr>. We would modify examples accordingly, and we would deprecate use of <biblScope> inside of <imprint>.
There would be no change to the definition or examples of <extent>: it would still be used not for mentions of particular pages or volumes but for a statement like "4 vols." and "325 pages".