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NEW ISSUE: example for matching functions, was: Weak and strong ETags

From: Julian Reschke <julian.reschke@gmx.de>
Date: Sat, 02 Dec 2006 12:34:16 +0100
Message-ID: <457164B8.2040203@gmx.de>
To: ietf-http-wg@w3.org

Hi,

given the fact that more than a few persons were confused about the weak 
matching function, I'd propose to add an example here, to appear below 
the definitions in 13.3.3:

     The example below shows the results for a set of entity tag pairs,
     and both the weak and strong comparison function results:

          +--------+--------+-------------------+-----------------+
          | ETag 1 | ETag 2 | Strong Comparison | Weak Comparison |
          +--------+--------+-------------------+-----------------+
          | W/"1"  | W/"1"  | no match          | match           |
          |        |        |                   |                 |
          | W/"1"  | W/"2"  | no match          | no match        |
          |        |        |                   |                 |
          | W/"1"  | "1"    | no match          | match           |
          |        |        |                   |                 |
          | "1"    | "1"    | match             | match           |
          +--------+--------+-------------------+-----------------+

Best regards, Julian



Julian Reschke schrieb:
> 
> Henrik Nordstrom schrieb:
>> tor 2006-11-30 klockan 20:03 -0800 skrev Wilfredo Sánchez Vega:
>>
>>>    Two, I don't think you can assume that "X" and W/"X" are at all  
>>> related to each other.
>>
>> HTTP specs do... see RFC2616 13.3.3, The weak comparison function.
> 
> You are right. However, the fact that this discussion has been going on 
> for almost one year now, and nobody mentioned that before, may indicate 
> that RFC2616bis potentially could make that clearer.
> 
>>> In Apache's case, there is no such guarantee,  because the same weak 
>>> ETag may be issues to different versions of the  document (if it is 
>>> edited more than once in the same 1-second window),  the data you got 
>>> with an ETag of W/"X" may be completely different  than the data that 
>>> later exists with an ETag of "X", or even the same  W/"X" you got.
>>
>> Then Apache is somewhat broken.
> 
> Yes, at least when the resource can be authored.
> 
>> Two identical weak etags SHOULD only be used if the objects is
>> semantically equivalent, but not necessarily octet equivalent. Two
>> different edits can not be considered semantically equivalent in this
>> context.  RFC 2616 13.3.4.
>> ...
> 
> Best regards, Julian
> 
Received on Saturday, 2 December 2006 11:34:25 GMT

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