Commit #130404 by robertDouglass at 16:25
Export DocBook: /modules/export_docbook/h2db.xsl 1.1.4.15 @ DRUPAL-5
Support for end-of-book indexes. This is a bit of a hack but works well enough for most purposes. To make an end-of-book index you need two things. An <index/> tag somewhere in the book (this now gets added), and <indexterm> elements in the Docbook XML. The trick here is twofold. <indexterm> elements can have <primary>, <secondary> and <tertiary> elements that make nice nested indexes. No HTML element follows this pattern semantically, so there is no 1-1 mapping that can be made. My solution is to use an <ol class="docbook-index"> like this:
<ol class="docbook-index">
<li>Primary term</li>
<li>Secondary term</li>
<li>Tertiary term</li>
</ol>

Of course this shouldn't render in HTML so the current solution will be to render exactly that type of element with that class as display:none. Hope it's a good enough hack for the time being!