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

From: Brian McBride <bwm@hplb.hpl.hp.com>
Date: Thu, 10 May 2001 11:07:41 +0100
Message-ID: <3AFA686D.7C02A4FC@hplb.hpl.hp.com>
To: fmanola@mitre.org
CC: w3c-rdfcore-wg@w3.org


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
Received on Thursday, 10 May 2001 06:08:02 EDT

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