Re: ETag and resource representations

On 14.08.2013, at 16:23, Erik Wilde <[email protected]> wrote:

> hello jan.
> 
> On 2013-08-14 16:11 , Jan Algermissen wrote:
>> On 14.08.2013, at 03:11, Hubert A Le Van Gong <[email protected]> wrote:
>>> I have a question about associating ETag to resources in a REST-based architecture.
>>> Would you recommend associating a single ETag to the canonical (i.e. complete) resource or rather use a different ETag for each representations of said resource.
>>> For instance, if I consider a library (full of books) as a resource. The view of that resource (i.e. the list of books returned) may vary based on the age of the reader (or any other criteria). Should I consider one ETag for the library as a whole or should I create an ETag for each representation returned to each reader?
>> ETag applies to the representation. If the actual bytes of the representation differ  the ETag must differ.
> 
> that's correct for strong ETags (the default), but not the case for weak ETags (which a server can choose to use).

Ahr yes, forgot these - thanks for point that out.  

For a deeper discussion: http://www.mnot.net/blog/2007/08/07/etags

Jan


> 
> http://tools.ietf.org/html/rfc2616#section-13.3.3
> 
> i'd say that weak ETags are mostly used to have ETags survive non-essential differences (hit counters are the canonical example). it would be interesting to hear whether services are using them for other purposes like the one hubert mentioned.
> 
> cheers,
> 
> dret.
> 
> -- 
> erik wilde | mailto:[email protected]  -  tel:+1-510-2061079 |
>           | UC Berkeley  -  School of Information (ISchool) |
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