W3C home > Mailing lists > Public > public-semweb-lifesci@w3.org > October 2007

Re: RFC 2616 vs. AWWW

From: Pat Hayes <phayes@ihmc.us>
Date: Thu, 11 Oct 2007 15:19:36 -0500
Message-Id: <p0623090fc334286fa7f5@[10.100.0.7]>
To: "Jonathan Rees" <jonathan.rees@gmail.com>
Cc: public-semweb-lifesci <public-semweb-lifesci@w3.org>

>For URI fanatics only...
>
>For the purposes of my URI project I wanted to know just what IANA had
>to say about the use of http: URIs, so I did some poking around. I
>report (neutrally, I hope) on what I found here:
>
>http://esw.w3.org/topic/HCLSIG_BioRDF_Subgroup/Tasks/URI_Best_Practices/Recommendations/StatusOfHttpScheme
>
>Jonathan

Well, seems to me you over-interpret what http/1.1 spec says.

-----
resource
     A network data object or service that can be identified by a URI, 
as defined in section 3.2. Resources may be available in multiple 
representations (e.g. multiple languages, data formats, size, and 
resolutions) or vary in other ways.
-----

Let us agree that 'identify' in HTTP1.1 documentation, and 'denote' 
(aka 'refer to') are separate notions. Then HTTP1.1 says nothing 
about what URIs *refer to*. Http-range-14 however says that for 
information resources, reference and identification must coincide 
(which retrospectively blesses the traditional confusion between 
these notions in this technical literature.)

In your example, we know that a URI refers to a potato. OK, but that 
says nothing about what it identifies. Http-range-14 says that the 
http endpoint for this URI ought to redirect it to some other 
resource which can emit a representation which somehow explains what 
the first URI does refer to. Give temporary names to all these things:

URI1  the first URI
endp    the http endpoint identified by URI1
URI2   the URI to which endp redirects URI1
redir   the http endpoint identified by URI2
potato  the potato which (we all know) URI refers to

Then the following should hold, according to http-range-14:

URI1 refers to potato
URI1 identifies endp
URI2 identifies redir
URI2 refers to endp (since endp is an 'information resource, the kind 
that HTTP1.1spec is talking about, so reference and identification 
coincide here)

and, hopefully, endp emits representations which explain the first of 
these facts.

But nothing here says that potato is the same as endp, or that a 
vegetable is handling a GET request. One could describe the situation 
as follows: the potato's name identifies a thing which one might call 
the potato's computational doppelganger: a network entity whose sole 
function is to catch any attempts to identify the potato, and toss 
them to another thing which can return some useful information about 
the potato. It could of course do this itself were it not for the 
unfortunate fact that, because of http-range-14,  this would probably 
confuse you into thinking that it actually was the potato.

Pat
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Received on Thursday, 11 October 2007 20:19:55 GMT

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