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Re: Multi-server HTTP

From: Mark Nottingham <mnot@mnot.net>
Date: Tue, 1 Sep 2009 12:32:02 +1000
Cc: Henrik Nordstrom <henrik@henriknordstrom.net>, "Ford, Alan" <alan.ford@roke.co.uk>, Robert Siemer <Robert.Siemer-http@backsla.sh>, ietf-http-wg@w3.org, Mark Handley <m.handley@cs.ucl.ac.uk>
Message-Id: <67FB6FD3-6B3F-4D2C-9C9A-FECF8D8F0168@mnot.net>
To: Anthony Bryan <anthonybryan@gmail.com>
That's a good start, but it deserves a bit of discussion.

"byte-for-byte" implies that the bodes are the same, but what about  
things like:

* Entity headers (e.g., Content-Type)
* Available content-encodings
* Whether partial content is supported
* Whether the same set of methods are supported (e.g., if A is a  
duplicate of B, will POSTing something to either have the same effect  
as on the other?)

I think the answer is that entity headers should generally be the  
same, so the real question is whether we're talking about the relation  
describing:

a) resources with duplicate representations (i.e., a GET on any of the  
dups will return the same reps)
b) duplicate resources (i.e., any method will have the same effect)

If it's (b), we should consider whether the resources are in fact the  
same "behind the curtains" (e.g., POSTing to A has the exact same  
effect on the world as POSTing to B), or whether they may be in fact  
separate systems (i.e., A and B have the same "interface", but POSTing  
to A may affect a different part of the world to B).

Just food for thought...



On 01/09/2009, at 6:03 AM, Anthony Bryan wrote:

> On Mon, Aug 31, 2009 at 3:39 AM, Mark Nottingham<mnot@mnot.net> wrote:
>
>> I don't think so; 'alternate' doesn't specify for what purpose it's  
>> an
>> alternate, and you need a very precise definition (byte-for-byte  
>> equivalence
>> of representations). 'alternate' is often used to mean "here's a  
>> copy in
>> another format" and similar.
>>
>> Perhaps you should mint 'duplicate'...
>
> Ok, this is what I have in the ID now:
>
> Link Relation Type Registration: "duplicate"
>
> o Relation Name: duplicate
> o Description: Refers to an identical resource that is a byte-for-byte
> equivalence of representations.
> o Reference: This specification.
>
> -- 
> (( Anthony Bryan ... Metalink [ http://www.metalinker.org ]
>  )) Easier, More Reliable, Self Healing Downloads


--
Mark Nottingham     http://www.mnot.net/
Received on Tuesday, 1 September 2009 02:32:46 GMT

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