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Re: ambiguity in BNF: no non-numeric TLDs?

From: by way of Martin Duerst <pk@TechFak.Uni-Bielefeld.DE>
Date: Thu, 13 Nov 2003 07:19:25 -0500
Message-Id: <>
To: uri@w3.org

Roy Fielding wrote:

 > > Can we assume that TLDs will be non-numeric?
 > Yes, but we can't assume that the last domain is a TLD.

there's no document I am aware of that explicitly precludes "numeric" TLDs.
RFC 1123, section 2.1 says "... at least the highest-level component label will
be alphabetic" but that's probably due to the fact that additional TLDs
were not yet on the table. I'd see that as descriptive instead of normative.
However, as a consequence, hostnames that look like IP addresses are
(obviously) not allowed, and operational wisdom will hopefully continue to
help this assumtion be true.

 > All of our attempts to disambiguate within the grammar itself did
 > not work because, without a trailing ".", there is no way to know
 > which is the TLD.

Again, the "." is not part of the domain name. It's a user interface issue,
as is using non-FQDNs. In the context of UR*, the "U" doesn't really make
sense for non-FQDNs.

Received on Thursday, 13 November 2003 07:36:59 UTC

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