DOCBOOK: Adding PDF to the <imagedata> format notations in version 5.0

Is there any possibility of adding PDF to the format notations for
<imagedata> in version 5.0?  

We find that using PDF images gives us high-quality graphics in PDF
output, even when scaled.  We're currently sneaking them in using the
<graphic> element, by not specifying a format and letting the stylesheet
find it. (See posting of 06/09/00 and 07/11/00 to docbook-apps list.)  

But in looking ahead to version 5.0, the <graphic> element will be
discarded.  If PDF can be added to the <imagedata> format notations our
life will be a lot easier.  

Thanks.

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Bob