local xref.role.attrib customization question?

["Carl E. Anderson" <cea@ncipher.com>]

Hi all,

I'd like to tack on a local customization of the role attributes for the 
xref element to my local copy of the docbook DTD.  Where I work, we have 
a few other local customizations that are defined in a "main.dtd" file 
(which is loaded before anything else) that then references the standard 
DocBook DTD for everything else (so that, of course, we can update 
DocBook as standard without losing our local tweaks).  I'm very 
inexperienced in these sort of things, so I thought I would solicit 
advice here :)

Basically what I want to do is predefine the available values for the 
xref's role attribute without actually mucking up dbpoolx.mod.  I see 
from looking at that file that the xref attlist looks like:

<!ENTITY % xref.attlist "INCLUDE">
<![%xref.attlist;[
<!ATTLIST xref
		endterm		IDREF		#IMPLIED
		%linkendreq.attrib;		%common.attrib;
		%xref.role.attrib;
		%local.xref.attrib;
 >
<!--end of xref.attlist-->]]>

... and that xref.role.attribute looks (very dull) like:

<!ENTITY % xref.role.attrib "%role.attrib;">

and that role.attrib looks (also very dull) like:

<!ENTITY % role.attrib
	"role		CDATA		#IMPLIED">

So, I guess what I'm trying to figure out is whether I add something to 
prescribe values for xref.role.attrib to my local "main.dtd" file 
customizations that will override the lack of prescribed values in 
dbpoolx.mod but that doesn't actually require modifying dbpoolx.mod 
itself?  I've poked around with trying to define some entity that with 
my prescribed values for xref.role.attrib in my local "main.dtd" file, 
hoping they would override dbpoolx.mod, but though I don't seem to have 
broken anything, I also haven't achieved what I wanted ;)

I suppose I should just go ahead and modify dbpoolx.mod and make a note 
so that I can reproduce the changes after future updates from standard 
DocBook -- but that seems inelegant!  Any thoughts?

Cheers,
Carl

-- 
Carl E. Anderson  mailto:cea@ncipher.com  http://www.ncipher.com/
nCipher Corporation Ltd.   +44 1223 723690   Fax: +44 1223 723601