Content reference to fragments

["Paul Prescod" <paul.prescod@blastradius.com>]

One of our customers would like to have content references of the form:

Maintopic.xml:

<!DOCTYPE topic ...>
<topic>
...
<p conref="fragment.xml">...</p>
</topic>

Fragment.xml:

<!DOCTYPE p ...>
<p>A paragraph</p>

Am I correct in my understanding that DITA disallows this? The
architecture reference implies (but does not say) that conrefs must
refer to elements by IDs. The section "Identity Attribute" also implies
(but does not say) that all DITA information must always reside within
either topics or maps. I would suggest that the architecture
specification have a formal definition of "DITA document" that either
(preferable, IMO) allows or disallows documents with other root types.
If it allows them then it should be possible to conref them and conref
into them.
----
 Paul Prescod
 Blast Radius XMetaL