For an explanation of what that rule means, from one of the folks who
defined it, see Tim Bray's _Annotated_XML_Specification_. One copy can
be found at
http://www.xml.com/axml/testaxml.htm
If you scroll or search down to "Well-Formedness Constraint: No External
Entity References", then click on the "(T)" icon following that
sentence, the second window will bring up the justification for why it
really does mean exactly what it says.
The Annotated XML Spec, by the way, is an absolutely invaluable resource
if you're trying to figure out what the spec really means, or why it is
as it is, or if you just want to better understand the philosophy behind
the original design of XML. Highly recommended resource. The only
complaint anyone has been able to make is that it's specifically based
on XML 1.0... and Tim Bray has said that he simply doesn't have the time
and energy to tackle updating it for XML 1.1.
By the way, when reading W3C specs, don't forget to check the errata
documents too. Sometimes there is newer information there, and often the
history of how the document has been clarified is enlightening... at
least for us language lawyers. (Reading specs is a skill worth
acquiring, by the way.)
--
() ASCII Ribbon Campaign | Joe Kesselman
/\ Stamp out HTML e-mail! | System architexture and kinetic poetry