keyref attribute on non-titled non-linked container elements

Hi, Working through the attribute tables, I've so far encountered three container elements in the BookMap specialization that use keyref.
These are explicitly non-titled, non-linking container elements: <frontmatter>, <backmatter>, and <booklists>.
These specialized elements explicitly disallowed @navtitle (when there was no <navtitle> equivalent); they also disallow @href because they are not intended to reference a topic.
The specialization left @keyref, but it's worth nothing this was DITA 1.1 (keyref was still undefined).
So the question is - what does @keyref mean on these three elements?
It uses the common definition in our spec, but that should really be modified to something narrower (even if we state that it is undefined for these three elements).
Robert D Anderson IBM Authoring Tools Development Chief Architect, DITA Open Toolkit ( http://dita-ot.sourceforge.net/ )