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"Variant" language in Content-Location (Issue 109)

From: Julian Reschke <julian.reschke@gmx.de>
Date: Tue, 05 Aug 2008 21:54:24 +0200
Message-ID: <4898AFF0.5020007@gmx.de>
To: HTTP Working Group <ietf-http-wg@w3.org>

Hi,

I was staring at the definition of Content-Language, and trying to 
figure out how to rephrase it avoiding the term "variant" (as discussued 
in <http://wiki.tools.ietf.org/wg/httpbis/trac/ticket/109>):

RFC 2616 says:

    The Content-Location entity-header field MAY be used to supply the
    resource location for the entity enclosed in the message when that
    entity is accessible from a location separate from the requested
    resource's URI. A server SHOULD provide a Content-Location for the
    variant corresponding to the response entity; especially in the case
    where a resource has multiple entities associated with it, and those
    entities actually have separate locations by which they might be
    individually accessed, the server SHOULD provide a Content-Location
    for the particular variant which is returned. -- 
<http://tools.ietf.org/html/rfc2616#section-14.14>

Comments:

- the first "MAY" seems to be useless and actually distracting ("may be 
used", "can be used" or "is used" would be just fine)

- "...when that entity is accessible from a location separate from the 
requested resource's URI" -- can this be simplified to "when that entity 
is accessible from a location separate from the request-URI"? Or am I 
missing something here?

- then it goes on saying server "SHOULD" return the header, but then 
"SHOULD return especially" in some special cases -- but there was 
already an unconditional SHOULD without that condition.

Part of this confusion seems to be the result of trying to BCP14fy what 
RFC2068 said (which had the first "SHOULD" in lower case).

So, looking at RFC 2068:

    The Content-Location entity-header field may be used to supply the
    resource location for the entity enclosed in the message. In the case
    where a resource has multiple entities associated with it, and those
    entities actually have separate locations by which they might be
    individually accessed, the server should provide a Content-Location
    for the particular variant which is returned. In addition, a server
    SHOULD provide a Content-Location for the resource corresponding to
    the response entity. -- 
<http://tools.ietf.org/html/rfc2068#section-14.15>

This looks a bit better, except for the last sentence:

"In addition, a server SHOULD provide a Content-Location for the 
resource corresponding to the response entity."

...which I frankly do not understand -- what does it say what hasn't 
been said before?

So if I had to rewrite this I would make it just:

    The Content-Location entity-header field may be used to supply the
    resource location for the entity enclosed in the message. In the case
    where a resource has multiple entities associated with it, and those
    entities actually have separate locations by which they might be
    individually accessed, the server SHOULD provide a Content-Location
    for the particular variant which is returned.

(BCP14fying the should, dropping the last sentence)

Feedback appreciated,

Julian
Received on Tuesday, 5 August 2008 19:55:08 GMT

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