Default Topic in Help Output

Greetings colleagues

A recent question on the Yahoo! DITA Users list was about how to nominate a
topic other than the first topic as the default page in a CHM output using
the DITA OT. Deborah Pickett provided a workaround solution, which was to
adjust the DITA OT map2hhp.xsl file, and to mark up the topicref of the
default topic in the ditamap with a specific outputclass attribute (eg,
"start-topic").

It occurs to me that this is likely to be a common requirement for all
tri-pane outputs. To support a nominated default topic option without using
this outputclass workaround would require a specification change, I believe.
To be thorough, we would probably need to consider a home topic option as
well; that is, the topic that displays when the Home button in the tri-pane
is pressed. So that would mean there are three "first" or "top" topics: 

. the first topic in the map (and therefore in the TOC tree)
. the first topic displayed when the Help is opened
. the topic that is displayed when Home is selected.

It seems logical that this information should reside in the ditamap. I'm not
sure whether its logical location is as an attribute of the topicref
element, though. 

Any thoughts?

Tony Self