Re: Entity Tags

Addressed to: Gavin Button <gavinb@imaging.co.uk>
              "'www-talk@w3.org'" <www-talk@w3.org>

** Reply to note from Gavin Button <gavinb@imaging.co.uk> Mon, 12 Aug 1996 17:02:01 +-100 
 
 
> I am in the process of designing an HTTP 1.1 server which  provides  
>  JPEG Images when a GET method with a certain URL is received, but am unsure  
> about the use of entity tags.  Should an entity of this type respond with an ETag  
> field ? In turn, should I support If-Match/If-None-Match? If so ,How? 
 
Yes. 
 
Yes. If you're going to supply an Etag then you need to support 
If-Match and If-None-Match. There's no need for an Etag unless you 
do since the client request must use those headers to make 
conditional requests. 
 
Just match on the Etag when a request comes in. The Etag is an 
opaque identifier to the sender, so you may use any unique id 
for the image. 
 
Just remember to allow for *both* If-Match and If-None-Match 
headers in the same request. It's also possible, although stupid,  
that you may receive the same Etag in both headers by a  
confused client/proxy. 
 
Paul 


Paul Hethmon 
phethmon@utk.edu 
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Received on Monday, 12 August 1996 14:01:49 UTC