Should Nested Topicrefs Be Allowed for format="ditamap"?

I'm implementing my own chunk to-content processing and as a side effect 
of that implementing map-to-map refs. It occurred to me that having 
something like this:

<topicref href="submap-01.ditamap" format="ditamap">
   <topicref href="foo.dita"/>
</topicref>

Doesn't make a lot of sense since it's somewhat ambiguous where the 
subordinate topicref would effectively be relative to the contents of 
the target ditamap.

I think this case should be disallowed but I haven't thought about it 
that deeply.

This use of topicref has always seemed a little iffy to me. I would be 
happier with a new construct that was explicitly a map-to-map reference 
but I realize it's probably too late to make that design change for 1.2, 
if it would be appropriate to make it at all.

But I think we should clarify the constraints in this case: either 
disallow the case above or state clearly what the effective result is.

Cheers,

Eliot

-- 
Eliot Kimber
Senior Solutions Architect
"Bringing Strategy, Content, and Technology Together"
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