Dominique Hazaël-Massieux wrote to <mailto:www-validator@xxxxxx> on 17
August 2004 in "Re: suggest validator prefer URI to FPI"
(<mid:1092749701.4811.155.camel@stratustier>):
SYSTEM identifiers may be dereferenced, but needs not be. As such, they
are probably more interesting than public ones, with which you can't do
anything if you don't know them.
This is false. All SGML/XML formal public identifiers (FPIs) are
isomorphic to URIs in the 'urn' namespace 'publicid' [1]. The
conversion from one form to the other is precisely defined.
So, assuming that I can't query the Web directly about a formal public
identifier, I can translate the formal public identifier to a URI
(which happens to be a URN of the 'urn' scheme) and query the Web about
the URI.
[1]
Norman Walsh; John Cowan; Paul Grosso.
"A URN Namespace for Public Identifiers".
August 2001.
Internet Engineering Task Force Request For Comments (RFC) 3151.
<urn:ietf:rfc:3151> (at various locations).
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