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Re: ldp-ISSUE-10 (Guidance around ETags): Include clarifications and guidance around ETags [Linked Data Platform core]

From: Henry Story <henry.story@bblfish.net>
Date: Sun, 3 Feb 2013 19:15:11 +0100
Cc: "Linked Data Platform \(LDP\) Working Group" <public-ldp-wg@w3.org>
Message-Id: <9F84DA75-896F-46DC-AE63-1C82F6D99C24@bblfish.net>
To: Steve Battle <steve.battle@sysemia.co.uk>

On 3 Feb 2013, at 18:19, Steve Battle <steve.battle@sysemia.co.uk> wrote:

> ETags (entity tags) can be strongly or weakly validating:
> 
> A strong ETag match indicates byte-for-byte, syntactic equivalence.
> A weak ETag match indicates semantic equivalence.
> 
> For RDF models, semantic equivalence is more important than strong syntactic equivalence. The same RDF content can be serialized in many different, but semantically equivalent ways. This is true even where the same serialization format is used.
> 
> * I propose that an LDP server should return only _weak_ ETags for LDP Resources and Containers. 
> * For other kind of resources then _strong_ eTags should be used.
> 
> Weak ETags are prefixed with 'W/'.
> e.g. "W/1234567890" instead of "1234567890"

Ah thanks for pointing this out. I did not know. 
For others:

   http://tools.ietf.org/html/rfc2616#section-3.11

certainly for graph resources it makes more sense to use weak
e-Tags, and so especially if one were to create a  :weakEtag relation
on an LDPR it would be the type of relation one could use
when describing things in a container or in a metadata file 
( the atom-entry file )


> 
> Steve.
> 
> 
> On 2 Oct 2012, at 15:13, Linked Data Platform (LDP) Working Group Issue Tracker <sysbot+tracker@w3.org> wrote:
> 
>> ldp-ISSUE-10 (Guidance around ETags): Include clarifications and guidance 
>> around ETags [Linked Data Platform core]
>> 
>> http://www.w3.org/2012/ldp/track/issues/10
>> 
>> Raised by: Raúl García Castro
>> On product: Linked Data Platform core
>> 
>> "4.1.13 BPR server responses must contain accurate response ETag header 
>> values."
>> 
>> I don't know what "an accurate response" means in this context. Maybe the 
>> intention is to say that strong entity tags MUST be used (and not weak 
>> ones).
>> 
>> If so, I would rewrite this as: "BPR server responses MUST use strong entity 
>> tags as response ETag header values.".
>> 
>> This issue may also include the comments made about the use of ETags by 
>> Leigh Dodds 
>> (http://lists.w3.org/Archives/Public/public-ldp-wg/2012Jun/0013.html) and 
>> Steve Speicher 
>> (http://lists.w3.org/Archives/Public/public-ldp-wg/2012Jul/0006.html) which 
>> led to the need of "crafting the right set of guidance around ETags".
>> 
>> 
>> 
> 
> 

Social Web Architect
http://bblfish.net/



Received on Sunday, 3 February 2013 18:15:44 UTC

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