question regarding book numbering in DITA/DocBook

A question was raised during today's DITA TC meeting about how DocBook 
handles ISSN and ISBN numbers.

This information is contained inside bookinfo/isbn (see  
http://docbook.org/tdg/en/html/isbn.html) and bookinfo/issn (see 
http://docbook.org/tdg/en/html/issn.html) elements.

There are also several other elements intended for numbering: 
invpartnumber, issuenum, pubsnumber, seriesvolnums, and volumenum

Best regards,
-- Scott