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Re: "semantics" of URI

From: Graham Klyne <GK@ninebynine.org>
Date: Fri, 06 Jun 2003 22:11:35 +0100
Message-Id: <>
To: "Roy T. Fielding" <fielding@apache.org>, "Larry Masinter" <LMM@acm.org>
Cc: <uri@w3.org>


I'm rather with Larry on this one.  I think "semantics" means slightly 
varying things to computer scientists and logicians/philosophers.  Larry's 
suggestion has the advantage of isolating the essential issue of 
identification/denotation without getting drawn into differing views of 

Also, I think the apparent plurality of "semantics" is a red herring.  From 
my dictionary:
semantics // n.pl. (usu. treated as sing.)
the branch of linguistics concerned with meaning.
A singular noun form is not listed.


At 12:20 06/06/03 -0700, Roy T. Fielding wrote:

>On Friday, June 6, 2003, at 11:42  AM, Larry Masinter wrote:
>>>2.3, 1st para after BNF block.  "Unreserved characters can be escaped
>>>without changing the semantics of a URI".  This is at best highly
>>>misleading in the case of URIs used as XML namespace names, whose only
>>>semantic is identification and comparison, and where comparison is
>>>typically done using strcmp(), and thus escaping an 'a' character will
>>>indeed change its semantics.
>>>That isn't a semantic.
>>I think we might improve the situation by avoiding using the
>>phrase "the semantics of a URI". It's been made clear in many
>>circumstances that "semantics" is a heavily loaded
>>word, and that use of "the semantics of a URI" presupposes
>>that there might be a single "semantics" associated with a
>>URI string.
>I don't see how that would improve anything.  If there were a single
>semantic then it wouldn't be plural.
>>First, this document shouldn't be defining "semantics" except
>>to give the URI scheme definition the opportunity for doing so,
>I disagree.  There are many semantics having to do with identifiers
>that are independent of scheme and cannot under any circumstances
>be voided by the scheme.  Those semantics are defined here.
>>and second, the only claim to "semantics" should be restricted
>>to the process of resource identification. URI strings
>>may also be involved in some other operations that involve
>>"semantics" (such as namespace names, or tokens in RDF),
>>and RFC 2396's definition need not interfere with those
>Again, I disagree.  If we allow a false semantic to be available
>to the implementer as if it were an option, then implementations
>may create dependencies on that falsehood.  We are better off telling
>the implementer that it is wrong and then letting them judge whether
>or not the false negatives are worth the gain in efficiency.  They
>still must be told the negative is a false one, because it will
>bite them in practice if they assume those two URIs are different.
>>So I suggest changing 2.3, 1st para after BNF block to read:
>>"Unreserved characters can be escaped without changing
>>  the semantics of a URI"
>>"Escaping unreserved characters in a URI should not change
>>  the resource identified."
>"does not" or "must not" is more appropriate.  I will make that change.
>>or even more accurately:
>>"URI schemes should be defined such that the escaping of
>>  unreserved characters does not change the resource identified."
>These rules are supposed to be scheme-independent.

Graham Klyne
PGP: 0FAA 69FF C083 000B A2E9  A131 01B9 1C7A DBCA CB5E
Received on Friday, 6 June 2003 17:15:05 UTC

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