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Re: 2002-02-25#19, Fragment identifiers, words for the primer

From: Graham Klyne <Graham.Klyne@MIMEsweeper.com>
Date: Tue, 12 Mar 2002 21:43:43 +0000
Message-Id: <5.1.0.14.2.20020312213053.039ab2f0@joy.songbird.com>
To: Aaron Swartz <me@aaronsw.com>
Cc: RDF Core <w3c-rdfcore-wg@w3.org>
At 01:18 PM 3/12/02 -0600, Aaron Swartz wrote:
>On 2002-03-12 1:11 PM, "Graham Klyne" <GK@NineByNine.org> wrote:
>
> >> This contradicts some readings of the URI specification[RFC2396], so 
> caution
> >> is recommended when creating new RDF terms which use fragment identifiers.
> >
> > I think that's too strong, on two counts "contradicts" and
> > "caution".
>
>It may be strong but I believe it's true (I'm interested in evidence to the
>contrary).
>
>Your on the other hand is false, or is at least misleading. (Specifically
>your claim that RFC2396 focuses on document retrieval. It is very clear
>about describing URIs in the abstract sense.)

False?  Misleading?  OK, here's what I said:

[[[
The URI specification [RFC2396] describes URIs with emphasis on their use 
for Web document retrieval, so be aware that the RDF use of fragment 
identifiers may appear to vary in some respects.  In particular, when using 
RDF, do not assume that a URI with fragment identifier denotes a part of a 
document identified by the base URI.
]]]

Section 4.1 of RFC 2396 starts with this text:

[[[
4.1. Fragment Identifier

    When a URI reference is used to perform a retrieval action on the
    identified resource, the optional fragment identifier, separated from
    the URI by a crosshatch ("#") character, consists of additional
    reference information to be interpreted by the user agent after the
    retrieval action has been successfully completed.  As such, it is not
    part of a URI, but is often used in conjunction with a URI.

       fragment      = *uric

    The semantics of a fragment identifier is a property of the data
    resulting from a retrieval action, regardless of the type of URI used
    in the reference.  ...
]]]

Which I think has a fair degree of emphasis on document retrieval.

I will concede that I might better have suggested this:

[[[
The URI specification [RFC2396] describes URI fragment identifiers with 
emphasis on their use with Web document retrieval, so be aware that the RDF 
use of fragment identifiers may appear to vary in some respects.  In 
particular, when using RDF, do not assume that a URI with fragment 
identifier denotes a part of a document identified by the base URI.
]]]

OTOH, your statement contains the essential ingredient of subjective 
interpretation ("some readings of") that pretty much guarantees it to be 
true.  I think it's too strong because:

(a) it suggests (by the word "contradiction") that there is a conflict 
between RDF and RFC 2396.  What I have come to perceive is that there isn't 
a conflict, just a reuse of a syntactic construct in a different 
context.  Arguably, RDF was unwise to use fragment identifiers in this way, 
but that's now water under the bridge.

(b) the form of words suggests that people should not be using fragment 
identifiers in RDF resource identifiers.  This advice would be inconsistent 
with the existence of rdf:id, hence confusing.

#g


-------------------
Graham Klyne
<GK@NineByNine.org>
Received on Tuesday, 12 March 2002 16:56:14 EST

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