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Re: network endpoints

From: <noah_mendelsohn@us.ibm.com>
Date: Wed, 30 Apr 2008 18:34:33 -0400
To: Jonathan Rees <jar@creativecommons.org>
Cc: "public-awwsw@w3.org" <public-awwsw@w3.org>, "Williams, Stuart (HP Labs, Bristol)" <skw@hp.com>, Tim Berners-Lee <timbl@w3.org>
Message-ID: <OF4AEC6626.6288B2B8-ON8525743B.007A1C45-8525743B.007BEA56@lotus.com>

Jonathan Rees wrote:

> I might have talked about servers, but was discouraged from 
> doing so by Stuart and Noah.

It was not my intention to discourage you from talking about servers, 
though I'm not yet convinced that they're an important abstraction in 
telling the basic HTTP story.  Maybe they are.  I was discouraging the 
introduction of the term "endpoint", which I understood (perhaps 
incorrectly) to be an abstraction for something that's not quite the 
server or the resource, but is also persistent in the sense that, unlike 
representation, it exists outside the context of one particular HTTP 

> An IR defined to be one whose awww:representations convey the 
> declaration of US independence isn't real in the same way since
> it would have those 
> awww:representations regardless of what happened on the web.

I'm not quite sure that the representations follow directly from the fact 
that the resource is the Declaration of Independence, but if there's an 
abstraction missing in the story I'm inclined to think that it may be the 
"assignment authority" or if you like the "owner" of the resource.  Let's 
say that I, Noah, have registered noahmendelsohn.com (I have) and that I 
choose to assign the URI 
http://noahmendelsohn.com/declarationofindependence.  I decide that the IR 
that I choose for this to represent is the text of the Declaration of 
Independence, including the lexical distinction of the front matter, the 
paragraphs, the signatures and so on.  I think I still have some freedom 
to decide which of the many (actually infinite) number representations of 
this information I will chose to serve.  For example, I could use large 
fonts or small, or a different type face.  I could send a text/html 
document and/or text/plain, etc.  All that's required is that the receiver 
be able to answer to come to agreement with me on the aspects of the 
representation I care about.  Crucially, it's not in general possible for 
a user retrieving a representation to determine whether the font size, for 
example, is something that I consider fundamental to the information 
content of the resource, or just an artifact of the representation I have 
chosen.  We can either model that by saying )a)that the resource is just 
the declaration, and that the particular representations served are 
determined by the responsible authority or (b) we can say that the 
resource is not in fact the Declaration in the abstract, but rather the 
particular representations, including choice of media types font 
specifications, etc.

Either way, I don't find "server" or "endpoint" to be the missing 
abstraction; "resource authority" or if you prefer "assignment authority" 
might be something we have to talk about.  If the authority chooses to use 
the mechanisms of some server software to create or choose the 
representations, so be it, but that's valid only because he/she chooses to 
delegate that responsibility.


Noah Mendelsohn 
IBM Corporation
One Rogers Street
Cambridge, MA 02142
Received on Wednesday, 30 April 2008 22:34:17 UTC

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