Re-use in DocBook

[<Ludger.Thomas@iese.fraunhofer.de>]

Dear all,
I have a question regarding multiple re-use of elements in DB. Hope I
manage to express what I mean.

Currently we are heavily working with entities + very modular XML files
which we aggregate to books, articles etc. using xi:include. This works
fine but nodes may only be included once (due to unique ID).

I wonder which ways exist to realize multiple usage of modular
information chunks in DB. I read about using the DITA maps, conref
method etc. but I'm not quite sure how and if this works. How would
xref, indexterm etc. be handled in case of multiple occurrences in DB?

What I had in mind for my document was to realize a model which might
look like this (abstract non-DB example, idea picked up from IMS
Manifest structure):
<root>
<organization> My Structure A
	<item resourceRef="res1"/>
	<item resourceRef="res2">
		<item resourceRef="res1"/>
	</item>
</organization>
<organization> My Structure B
	<item resourceRef="res2"/>
</organization>
<resources>
	<resource id="res1" .../>
	<resource id="res2" .../>
</resources>
<root>

I'd be curious to hear your comments if and how such multiple re-use of
resources could be realized in DB. My current alternative is to put all
resources in an appendix and make some references if they are used. But
I'd prefer to have the information in place and not only as a reference.
So I'd need some kind of transclusion.

Any ideas or comments? Has anybody realized such a document in DB? How
do you manage re-use in DB?

Best wishes.
Ludger Thomas