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- From: "Jonathan Borden" <firstname.lastname@example.org>
- To: <email@example.com>
- Date: Mon, 31 May 1999 23:26:47 -0400
Carl Hage wrote:
> I think the URI identifying namespaces and DTDs should be URLs
> not URNs. An XML document without retrievable documentation on
> the DTD should be considered non-compliant.
By definition XML namespace URI's are URNs *not* URLs regardless of which
URI scheme/namespace they use.
Quoting from RFC 2396 (note that this supercedes the definition of URL!!!):
A URI can be further classified as a locator, a name, or both. The
term "Uniform Resource Locator" (URL) refers to the subset of URI
that identify resources via a representation of their primary access
mechanism (e.g., their network "location"), rather than identifying
the resource by name or by some other attribute(s) of that resource.
The term "Uniform Resource Name" (URN) refers to the subset of URI
that are required to remain globally unique and persistent even when
the resource ceases to exist or becomes unavailable.
A URN differs from a URL in that it's primary purpose is persistent
labeling of a resource with an identifier. That identifier is drawn
from one of a set of defined namespaces, each of which has its own
set name structure and assignment procedures. The "urn" scheme has
been reserved to establish the requirements for a standardized URN
namespace, as defined in "URN Syntax" [RFC2141] and its related
Note that when the string "http://www.w3.org/xxx" is used as an XML
namespace URI this is a URN not a URL by definition (the scheme remains
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