[xslt] Should I be loading DTDs?

[David Hyatt <hyatt apple com>]

I asked for some good XSLT test cases on my blog, and one of the ones 
presented to me can be found here.

http://astro.nickshanks.com/library/extrasolar.xml

The author pointed out that he had a link to an external DTD that 
defined entities, and suggested that the DTD should be loaded.  I'm 
basically looking for suggestions as to what the "correct" default 
behavior should be for Safari.  Should I tell libxml to load the 
external DTDs by default when parsing XSL stylesheets and XML docs that 
do transforms?

dave