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Re: A shot at http://www.w3.org/2000/03/rdf-tracking/Overview.html#rdfms-resource-sem antics

From: Graham Klyne <Graham.Klyne@Baltimore.com>
Date: Fri, 11 May 2001 16:24:48 +0100
Message-Id: <5.0.2.1.2.20010511161947.03ed2d70@joy.songbird.com>
To: Brian McBride <bwm@hplb.hpl.hp.com>
Cc: fmanola@mitre.org, w3c-rdfcore-wg@w3.org
I'm a little concerned about the direction of this talk of entities and 
resources.

I thought the URI spec was fairly clear that:

(a) a resource is a "conceptual mapping"

(b) an entity is a "bag of bits"

I took Brian's stab at a formalism as being a way to say that the 
"conceptual mapping" that is a resource can be represented as a function 
that returns an entity.

So, to me, it seems completely wrong to say that a resource can *be* an 
entity, even when there is only one entity associated with a resource.  (By 
"associated with", I mean that can be returned by the function 
representation of the resource.)

#g

At 11:07 AM 5/10/01 +0100, Brian McBride wrote:


>Frank Manola wrote:
> >
> > As I said in an earlier message, I think we need to clarify what
> > "entity" means in our discussions.  In particular, we need to
> > distinguish between the definition of "entity" in the HTTP spec (where
> > it is some payload that can be returned) and the definition in Brian's
> > model, where "Entities are things like web pages, numbers and trees in
> > the park".
>
>Exactly right.  I may be at fault here for overloading the term.
>
> > (If the Web develops to the point where accessing what's
> > identified by a URI can return a tree, I hope I get adequate warning
> > before doing it!)
>
>I understand there was at one time (1st Apr 19xx) an RFC including a
>mime type for matter transfer.  All I could find in a google search
>was a reference to a Simple Matter Transfer Prototol.
>
>
> >
> > I take Brian's model as being something like this (although Brian is the
> > ultimate source of wisdom for *his* model):
>
>You have expressed it very well.
>
>There are several such 'model theories' if that is the right term that
>will work for us.  I picked this one as it seemed to me most consistent
>with M&S.  However, I'm more concerned that we have agreed on one, than I
>am about any particular one.
>
>
> >
> > Finally, even though you can imagine two resources being mapped to the
> > same entity, if different people are doing the mappings, it isn't
> > necessarily going to be easy to decide when two resources are really
> > equivalent.
>
>That may well be true :(.  The reason for introducing equivalence was not
>so that we could mechanically decide that two resources are equivalent, but
>so that our model could represent equivalence.
>
>There isn't anything particularly deep here, its just about what we call
>things.  Web principles state that we can't rely on there being one true
>URI identifying a particular entity - e.g. tree in the park.  Anyone is
>free to define a URI to name this tree.  So we have a choice:
>
>   - Resources have more that one URI
>   - each URI identifies a different resource, but we have the notion
>     of equivalence classes of resources
>
>I felt that the latter is closer to M&S and RDF.
>
>Brian

------------------------------------------------------------
Graham Klyne                    Baltimore Technologies
Strategic Research              Content Security Group
<Graham.Klyne@Baltimore.com>    <http://www.mimesweeper.com>
                                 <http://www.baltimore.com>
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Received on Friday, 11 May 2001 13:33:46 EDT

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