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   Re: URNs as SYSTEM IDs

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  • From: Norman Walsh <ndw@nwalsh.com>
  • To: xml-dev@lists.xml.org
  • Date: Wed, 22 Nov 2000 14:57:23 -0500

/ "Simon St.Laurent" <simonstl@simonstl.com> was heard to say:
| In common practice, that's meant using URLs, typically HTTP-based URLs.
| Validating (and some non-validating) XML parsers tend to report errors when
| they can't retrieve the content referenced by a SystemLiteral, since
| effectively it means that they can't validate the document.

They can retrieve the content if they have some practical entity
management system in place, such as OASIS TR9401 Catalogs (through,
for example, a SAX entityResolver).

| I can't find a validity constraint which mandates this behavior, however.
| It seems like dereferencing is a fundamental quality of SystemLiterals, but
| that dereferencing is somewhat, well, variable.  Using URNs - when there
| isn't a whole lot of infrastructure for processing them - strikes me as
| foolhardy, but I can see where they might be attractive from an abstract
| perspective, at least.

At the very least, you should use a PUBLIC identifier as well since
that allows an entity manager to do the right thing even in the
presence of varying system identifiers.

                                        Be seeing you,

Norman.Walsh@East.Sun.COM | The stone fell on the pitcher? Woe to the
XML Technology Center     | pitcher. The pitcher fell on the stone? Woe
Sun Microsystems, Inc.    | to the pitcher.--Rabbinic Saying


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