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Re: removing constraints on 'resource' [024-identity]

From: Tim Berners-Lee <timbl@w3.org>
Date: Thu, 27 May 2004 15:58:33 -0400
Message-Id: <3B779F0E-B018-11D8-8039-000A9580D8C0@w3.org>
Cc: Dan Connolly <connolly@w3.org>, Stuart Williams <skw@hp.com>, uri@w3.org, Tim Bray <tbray@textuality.com>, Joshua Allen <joshuaa@microsoft.com>, msabin@milessabin.com
To: Pat Hayes <phayes@ihmc.us>

On May 27, 2004, at 11:02, Pat Hayes wrote:
[..]
> BTW, the diagram cited below (Im looking at the one at 
> http://www.w3.org/DesignIssues/diagrams/URI-space.png ) directly 
> embodies that confusion/ambiguity very clearly. There are two black 
> arrows at the bottom, one going from 'hypertext' to 'anchor', the 
> other going from 'semantic Web' to 'anything'. THESE TWO RELATIONSHIPS 
> ARE  NOT THE SAME KIND OF RELATIONSHIP. The first refers to 
> identification on a network, and belongs in my "C' category: the 
> second arrow is denotation, which has nothing to do with computation 
> and belongs entirely in the D category.

Yes.  The first is hypertext architecture; the second is semantic web 
architecture.  They are different.

A warning: read the diagram carefully: it is not a venn diagram of 
resources, but of URIs.
Sets -- subset of URIs -- are labeled in roman text, or typewriter text 
with syntactic constraints such as URI scheme.  Then, some regions in 
the diagram are annotated in italic with some examples of the things 
which can be *identified by* those URIs.   It is rather squeezed.  
"Anchor" should be in italics.

>  The first is supposed, by its very nature, be computable (given the 
> state of the network) and requires uniqueness of identification: 
> neither of these properties hold of the second. The second can refer 
> to anything: the first, by its very nature, cannot.  The second must 
> be understood relative to an interpretation: the first cannot be that 
> ambiguous but must be determined by the state of the Web.  The entire 
> force of my extended attempt to deconstruct the confusion in the TAG 
> architecture document can be summarized by the observation that these 
> two relationships, shown in this diagram by identical (and parallel) 
> arrows, are FUNDAMENTALLY DIFFERENT. 

Yes.

Actually the arrows show in URI space the mapping from a set of URIs 
without a hash to the set of URIs with hashes, specifically the mapping 
in which corresponds to appending a hash and something.  The syntactic 
relationship between the URIs is the same.  However, for hypertext and 
the semantic web architecture, the



>  Calling them both 'identification' is not a good strategy: it is in 
> fact little more than a pun. Applying criteria which make perfect 
> sense for one to the other produces nonsense and confusion.

No one is calling the arrow "+#localiD" "Identification".  
Identification is the relation between the URIs mapped in the venn 
diagram and things they are deemed to identify (as annotated from time 
to time in italics).


[...discussion of denotation skipped ...]

> Public discussion of http://www.w3.org/TR/webarch/ suggest that this
>  unconstrained definition of 'resource', along with a separate term 
> for a
>  smaller set of "information resources" is a useful way to describe 
> the role
>  of URIs in Web Architecture.
>
> Well, it might be if the document was rewritten carefully paying 
> attention to this distinction, and not applying advice suitable to the 
> special case to the more general case.

Yes indeed.

> However, the result would be that almost the entire document would be 
> about 'information resources'.

The editor has instructions to do the edit so we can see what it looks 
like.

> (we haven't finished the text yet, but you can see a diagram at
>   http://www.w3.org/2004/05/URI-space-small.png
>   http://www.w3.org/DesignIssues/diagrams/URI-space.svg
> and some notes on the discussion at
>   http://www.w3.org/2004/05/14-tag-summary.html#httpRange-14-1 )
>
>
>  The unconstrained definition of 'resource' is also what was imported 
> into
>  the RDF specification:
>
> Well, yes, but only because you told me that was obligatory, and in my 
> Webbish innocence I believed you :-)
>
>  Pat
>
>
>    The things denoted are called 'resources', following [RFC 2396], but
>    no assumptions are made here about the nature of resources; 
> 'resource'
>    is treated here as synonymous with 'entity', i.e. as a generic term
>    for anything in the universe of discourse.
>      -- http://www.w3.org/TR/rdf-mt/ aka
>   http://www.w3.org/TR/2004/REC-rdf-mt-20040210/
>
>
>  I think this captures the input I got from TimBL on the matter; could 
> you
>  confirm, TimBL?

Yes.

> [...]

> Dan Connolly, W3C http://www.w3.org/People/Connolly/
>
>
> -- 
>
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Received on Thursday, 27 May 2004 15:58:41 UTC

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