W3C home > Mailing lists > Public > www-tag@w3.org > July 2002

Re: fragment identifiers

From: Roy T. Fielding <fielding@apache.org>
Date: Tue, 23 Jul 2002 23:06:15 -0700
Cc: "Jonathan Borden" <jonathan@openhealth.org>, "Graham Klyne" <GK@NineByNine.org>, <www-tag@w3.org>, <timbl@w3.org>
To: "Joshua Allen" <joshuaa@microsoft.com>
Message-Id: <765E4F8C-9ECB-11D6-92C7-000393753936@apache.org>

On Tuesday, July 23, 2002, at 10:14  PM, Joshua Allen wrote:
> It's a "should", not a "must".  Systems that will "break" are systems
> which assume that an http: identifier identifies a hypermedia resource
> meant to be accessed via a web browser.
>
> People SHOULD use http: identifiers only to refer to resources which
> they intend to be accessed through HTTP.

That statement is not the same as "http URI SHOULD identify documents",
which is what we are having a disagreement about.

> Sorry to sound frustrated, but this is THE most important issue to the
> semantic web.  There is nothing more important than agreeing on an
> identification scheme that unambiguously (to the extent possible)
> identifies things.

How can it be THE most important issue when nobody can explain what
difference it makes to the Semantic Web?  Just saying it is important
doesn't get you anywhere.  I have no problem unambiguously identifying
things with any URI, including http, so I simply cannot fathom why
the topic keeps getting repeated.

>   I have commented on this issue on my personal web log:
> http://www.netcrucible.com/blog/2002/07/20.html#a225

Oh, for crying out loud!  I am going to try to explain this one more
time to see if it gets through and then I'll give up.

A URI is an identifier.  The semantics of the resource it identifies
are defined by the sameness of representations of that resource over
time, not by any property of the identification system used to create
that identifier. In short, a URI reference has the semantics that
other people assign to it when they persist in trying to use it to
refer to something useful.  This isn't a property of the technology;
it is a property of how people use the technology.  The same is
true of "words", whether or not you are prepared to admit it.
That is the basis of every modern human language except French.

Some identifiers are better (more persistent, more available, more
whatever-you-like) than others.  http identifiers are ideal for
resources that can be accessed through HTTP via TCP/IP.  Other
identifiers may be better for some cases, but only if they come
with a support infrastructure that makes them sufficiently useful
for people.  People decide what identifier is best for any given
situation, and it is a fundamental principle of the Web that
any URI scheme can be used as an identifier within any context or
protocol element that requires a URI.

XML namespaces, by the way, can be accessed through HTTP, as can
robots, climate controls, beaches, and any other thing for which
someone cares to provide a meaningful representation via HTTP.

> (Here is the exact same argument in human terms.  Sound like a Beckett
> play, doesn't it?)
> TimBL: People shouldn't say "bad" when they mean "good"
> Roy:   But people CAN use "bad" when they mean "good"; I heard
>        Michael Jackson do that before.

I'd appreciate it if you didn't use my name in a context that is
a deliberate deception on your part, since it will confuse readers
of the archive.  Besides, it makes you look like a total jack-ass.

....Roy
Received on Wednesday, 24 July 2002 02:06:54 GMT

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