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Re: Indicating a resource does not exist

From: Henry Story <henry.story@bblfish.net>
Date: Thu, 20 Jan 2011 16:01:17 +0100
Cc: Joe Gregorio <joe@bitworking.org>, HTTP Working Group <ietf-http-wg@w3.org>
Message-Id: <76BD702D-56BA-4AA4-995E-D318121E27E3@bblfish.net>
To: nathan <nathan@webr3.org>
On 20 Jan 2011, at 15:47, Nathan wrote:

> Joe Gregorio wrote:
>> On Thu, Jan 20, 2011 at 9:31 AM, Nathan <nathan@webr3.org> wrote:
>>> Joe Gregorio wrote:
>>>> What's wrong with 404 Not Found?
>>>  404 Not Found
>>>  ...
>>>  The server has not found anything matching the effective request URI.
>>>  No indication is given of whether the condition is temporary or
>>>  permanent ...
>>> 
>>> The best you can conclude from that is "don't know" the state of the
>>> resource, or if there is one.
>> OK, so 410 Gone if you want to indicate it is permanent.
> 
> 410 entails more though, "was a resource, is no longer a resource", 404 is "I don't know", I'm looking for an unambiguous "origin server says this is not a resource"
> 
> Essentially at the minute, the only resource states that can be conveyed (as far as I can see) are:
> 
> - created (POST/PUT 201, PUT 204)
> - current state (many combinations)
> - state changed (POST/PUT 200)
> - unknown state (DELETE 202, a few 3xx, most 4xx and all 5xx)
> - gone (204)
> 
> so basically, there's no way to say "no resource".

could be, and nobody has complained very loudly about this until now.
Do you have a use serious use case?

The problem with saying that a URI is not a resource, is that if it
does not dereference then that means that the server does not know
what it means. If the server does not know what it means, then how
can the server know that it is not a resource? You are touching
one one of those tricky philosophical problems, that could keep
you occupied for a lifetime if you are not careful. 

Perahps you could create a /dev/null url and have those resources
return

<> a <http://web3.org/ont/DevNull> .

Or you could have it be the empty set, which according to
David Lewis' latest book on mereology refers to the mereological
fusion of everything: every thing, every possible thing, every
possible world. ( see: Parts and Classes )

But then it would refer quite clearly to something, and you 
could use that something to build up all of mathematics on it.

Henry





> 
> Best,
> 
> Nathan
> 

Social Web Architect
http://bblfish.net/
Received on Thursday, 20 January 2011 15:02:17 GMT

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