[jats-list] BITS: Is there a canonical way to group multiple appendices and a glossary under a single 'Appendix' heading?

["Imsieke, Gerrit, le-tex" <gerrit.imsieke@xxxxxxxxx>]

There's a book whose backmatter consists of a glossary, two appendices 
and and index. In the printed version, the glossary and the appendices 
are contained in a book-part-like structure with the heading 'Appendix'. 
The index heading is intended to be on the same level as this 'Appendix' 
heading. The individual appendices below the 'Appendix' heading have 
their own distinct headings (let's call them 'Author Biographies' and 
'Handouts').

What is the canonical BITS way to encode this structure? I'll present a 
valid yet clumsy and an invalid variant.

Valid alternative:

  <book-back>
    <book-part dtd-version="0.2">
      <book-part-meta>
        <title-group>
          <title>Appendix</title>
        </title-group>
      </book-part-meta>
      <back>
        <glossary>
          <title>Glossary</title>
        </glossary>
        <app>
          <title>Handouts</title>
        </app>
        <app>
          <title>Author Bios</title>
        </app>
      </back>
    </book-part>
    <index>
      <title-group>
        <title>Index</title>
      </title-group>
    </index>
  </book-back>

I don't like that there's a book-part that could, in principle, host all 
kind of stuff that doesn't belong into a book's backmatter (front, body).

Or the use of a book-part in a book-back could lead you to think that 
the content now go into the book-part's body because you're already in 
the backmatter. Until you find out that an appendix or glossary can't be 
in the body.

Because I was kind of loath to use a book-part for the collective 
'Appendix', I thought of using app-group, like this:

  <book-back>
    <app-group>
      <title>Appendix</title>
      <glossary>
        <title>Glossary</title>
      </glossary>
      <app>
        <title>Author Bios</title>
      </app>
    </app-group>
    <index>
      <title-group>
        <title>Index</title>
      </title-group>
    </index>
  </book-back>

This looks more lightweight and appropriate in my view, except that 
glossary isnbt allowed in an app-group (only app elements are allowed 
there).

In principle, one could extract the glossary from the Appendix, leaving 
the two appendices proper under the Appendix heading, in an app-group. 
But if the glossary was moved before the appendices, there would be no 
'Appendix' heading before the glossary which probably isn't acceptable 
for the author and/or the publisher. If the glossary were moved past the 
appendices, the order in the electronic pulication (EPUB derived from 
BITS) would deviate from what's been printed, and this also seems 
unacceptable to some of the parties involved.

So is there a third way to encode this in a natural way, or do you 
consider the book-part way (first alternative) as a natural way already? 
Or do you also think (as I do) that there should be a generic container 
to group backmatter components? It could be app-group, but maybe with a 
book-part-meta instead of a mere title element.

What do you think?

Gerrit