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Re: Why distinguish entity vs. resource was: Re: [URI vs. URIViews] draft-frags-borden-00.txt

From: Jonathan Borden <jonathan@openhealth.org>
Date: Sun, 24 Feb 2002 21:44:27 -0500
Message-ID: <00bb01c1bda6$61759080$0301a8c0@ne.mediaone.net>
To: "Pat Hayes" <phayes@ai.uwf.edu>
Cc: <me@aaronsw.com>, <www-rdf-logic@w3.org>
Pat,

Note f/u to rdf-logic

> >
> >Imagine the resource that represents "Pat Haye's resume",
>
> Stop. What do you mean, *represents* a string of 18 characters ?

No, I mean your resume.

What
> I would give the URI to would *be* my resume, it wouldn't *represent*
> it. That is, my resume is a document, written in HTML, located at
> that network address.
>
> >you give it a URI:
>
> Its a URL, let us not mince words. I have never given anything a URI
> that wasn't a URL, myself.

Not mincing words. URL is a legacy term. It has been truly superceded by
URI. Of note, there are now network protocols that can resolve URNs, so the
URL/URN distinction is really really gone in all senses.

>
> >
> >http://pat.hayes.org/resume/
> >
> >Now suppose the Web had existed throught your early career. The actual
> >document returned by referencing the URI would change from time to time
as
> >additions are made to the resume.
>
> True. Now we have at least a three-way distinction to make.
>
> 1. The enduring 'thing' that is identified by the URL (I choose the
> 'L' deliberately)

let's call this the "resource"

> 2. The particular document(s) that might be obtained by HTTP GETting
> that URL at particular time(s)

let's call this the "document entity" or "entity"

> 3. The entities - resources, things, whatever one wishes to call them
> - which are identified by/described by/ denoted by/ named by/
> whatever the symbols in the retrieved document.
>

let's call these "nodes"

[snip]
>
> My own judgement is that the first of these is in fact not really a
> coherent idea. There are no 'resources' in this sense; such things
> would be like the 'soul of a true name' in Earthsea, but they don't
> exist in the actual world. The fact is, some referring expressions
> change their referents from time to time, like "the President of the
> USA" .  URLs, and file names more generally, do.  We just have to
> face up to this, and stop pretending that it isn't really true by
> inventing spurious things called 'resources' that never change. There
> is *nothing* that is guaranteed to stay constant when the document
> retrieved by a URL changes, other than the URL itself.

I agree completely. This is IMNSHO a critical point. I interpret it this
way:

The "resource" identified by a URI or a URIreference for that matter, is
nothing more than a node labelled by the string that is the URIref. For
every URIref, there is one and only one such node.

The terminology of "subresource" is perhaps specific to the use of URIs as
namespace names. A namespace really can be considered to contain a set of
nodes.

>
> BTW, this fantasy that URLs have been subsumed by things called URIs
> that are really not like old-fashioned global file addresses, but
> nowadays are elevated to a new status of being cosmically global
> IDENTIFIERS, is I think largely responsible for so much of the
> confusion. This is complete B.S., guys.

Not completely. What is real about this is that you can pay $ to a
registrar, which gives you a root name (DNS entry) and adds this name into
the DNS database that resolve the name to an IP address. This naming system
is used throughout the world, and most importantly has been accepted by the
legal system.

>
> >e.g. "resume" "home page" etc, The desire is to use
> >resources things not directly connected to the Web, nor easily
serializable,
> >such as a "person" or a concept such as "Unicorn", such resources are
termed
> >"abstract resources".
>
> What does 'use' mean in that sentence? If it means 'do something
> with', then wake up and stop smoking. If it means 'refer to', then
> fine: but then be careful not to confuse use and mention when talking
> about documents and things.

Generally I mean 'refer' however:

http://nasdaq.com/SELL?Stock=INTC&quant=1000

can have very very real consequences. More real than Unicorns.

Some of the resources refer to other
> resources, but only the former can actually be ON the web. Calling a
> unicorn a 'resource' doesn't make them suddenly computable; it just
> makes a semiotic claim to be able to talk about them. Which is
> *completely irrelevant* to the web, because all the web does is move
> representations around, in ways that have got *nothing whatever to do
> with* what those representations represent (except in the very
> special case where the representations are about other
> representations, like URLs.) The web is an inherently syntactic
> device.

This point is made up front in "REST". The owner of the DNS entry _can_
connect that URI to real actions, and particularly if you have a contractual
relationship with the owner, the resource in question can have a very real
monetary value. The point is that: the resource is what the owner of the DNS
entry says it is. Moving representations around _can_ have something very
much to do what the owner of the DNS entry says the resource is (e.g. a
place to buy or sell stock, a bank etc.) You can buy a house on the web.
This is very real. The courts say it is.

>
> >While an abstract resource is not connected to the Web, a
_representation_
> >of such a resource easily may be, e.g. a picture of you is available at a
> >given URI, or a picture of a Unicorn is available at
> >http://example.org/Unicorn.
>
> Agreed. But now you have to be careful. Who or what decides what
> exactly some representation is 'of'?

Specifically, "REST" says that the owner of the DNS entry says what the
resource is. How the SW will deal with such contractual issues remains to be
seen.

As far as any piece of software
> is concerned -  be it HTML or OWL - the best that can be done is that
> certain *kinds* of representation - text, XML/RDF, TIFF files,
> whatever - can be recognized and delivered to some engine that is
> able to use them appropriately. That is ALL it can possibly do. The
> engine must decide what to do with the representation (display it,
> color it green, process it in some way, draw conclusions from it,
> answer queries using it, whatever), and all that any kind of transfer
> protocol is able or required to do, is to deliver these
> representational packages on time and undamaged, as far as possible.
> The Web - http or semantic - is just a representation-delivery
> service.

Exactly. REST "REpresentation State Transfer" send a representation, change
a state.

All the rest - including anything at all to do with meanings
> or intended referents - is either the business of some specialized
> engine, or the business of some human mind. RDF is no different from
> any other web medium in this regard.
>
> >So again, the HTTP GET returns the
> >representation i.e. the entity, not the resource.
>
> Right, exactly. So the entire activity of the web is concerned with
> representations, not with resources. Let us get that carved in stone
> somewhere.  Now, to return to RDF and fragIds for a second, and
> bearing the above in mind, the (non)issue seems to be that RDF claims
> to be able to use names to refer to anything, but the
> transfer-protocol web world says that fragIds can only be used after
> the absolute URI has been used to retrieve a document. Fine; a
> non-issue. The former is an off-Web matter private to RDF inference
> engines. The latter is on on-Web matter, and there RDF acts just like
> HTTP, so there is no problem.
>
> >Does this make any sense?
>
> Well, the last part did :-)
>

Good. I don't think there is a real problem with what RDF does, and issued
an Internet Draft, merely to say:

"Hey, this is what RDF is doing, and it's ok."

Because ultimately I think that the SW will need to be connected to the
current Web in order to work, but that is just what I think.

Jonathan
Received on Sunday, 24 February 2002 21:09:55 GMT

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