W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > June 2001

Re: #rdfms-difference-between-ID-and-about (every document is in the Web)

From: pat hayes <phayes@ai.uwf.edu>
Date: Wed, 20 Jun 2001 18:13:45 -0500
Message-Id: <v0421011cb756dbfe52e1@[205.160.76.183]>
To: Dan Connolly <connolly@w3.org>
Cc: w3c-rdfcore-wg@w3.org
>Graham Klyne wrote:
> >
> > At 08:18 AM 6/15/01 -0500, Dan Connolly wrote:
> > >Graham Klyne wrote:
> > > >
> > > > At 02:29 AM 6/15/01 -0500, Dan Connolly wrote:
> > > > > > RDF absolutely has to make sense even outside the context of
> > > > > > an enclosing document which can be given a uri. so ...
> > > > >
> > > > >So... what? That doesn't make any sense to me.
> > > > >
> > > > >An RDF document is an XML document. Each XML document
> > > > >has a base URI (cf the infoset spec).
> > > >
> > > > If this is  true, then it is not possible to transfer RDF 
>data in transient
> > > > protocol elements.
> > >
> > >Why not? Transient things are resources too; you may or
> > >may not specify what their URI is (in the case
> > >of a mail messge, it would be mid:....); that doesn't mean
> > >they don't have one.
> >
> > Well, by definition (as I understand these things) it's only a resource if
> > it has a URI.
>
>I think you've slightly overstated the case there,
>but the argument holds even the way you've phrased it, so...
>
> > The fact that something can have a URI (and anything can, right?) doesn't
> > mean that it's got one.
>
>Suppose I say that it does. There's no argument to
>refute me, is there?

Well, I can refute you to my own satisfaction just by looking around 
my office at the books on the shelves.

>i.e. there's no reason not
>to adopt this as an axiom.

Other than it is obviously and immediately false, no. However, that 
is usually a pretty good reason to not adopt an axiom.

> > (Not every mail message has a Message-ID header,
> > from which the mid: is derived.)
>
>Those messages can be named just like all the things
>that aren't mail messages at all can be named.

They CAN be named, but (1) naming is not giving a URI to, and (2) 
even if they could be named, most of them havn't been, as a matter of 
fact. And some things couldnt possibly be named, by the way.

>
> >  From a practical viewpoint, having a URI but not knowing what it is
> > doesn't seem to be significantly different from not having a URI.
>
>But this isn't an issue of practical viewpoints; it's
>an argument of architectural constraints -- or rather,
>lack of them. So the difference is significant.
>
>You trust that I have a birthday even though you don't
>know it, right? By the same token, it seems easy
>enough to accept that resources have URIs even though
>those URIs aren't always specified.

But I know that every human has a birthday. I would guess that you 
own a shirt, but Im not absolutely certain; and I have no idea if you 
own, say, a VW beetle. Whereas I *know* that some email messsages 
don't have a URI.

>
> > > > Which means that (say) the CC/PP spec, formulated *by design* 
>as a *format*
> > > > only for client capability data, cannot be regarded as a valid RDF
> > > application.
> > >
> > >I don't see how that follows.
> >
> > Because (by my lights) a CC/PP profile may be some data that doesn't have a
> > URI.
>
>We disagree on that.
>
> >  Which (by your lights) means that it cannot be valid XML hence not
> > valid RDF.
> >
> > > > But what is the status of information that is not "on the Web"?
> > >
> > >Just think of everything as "on the Web".
> >
> > I don't.  That sounds to me more like a religion, or act of faith, than a
> > state of affairs.
>
>Well, that's how architecture and mathematics work, no?

No.

>i.e. by the same token, nothing compells you to agree that
>2+2=4, nor that the DNS has a unique root.
>But it follows from generally accepted axioms,
>so you do agree, right?

These are usually classified as necessary truths because they follow 
from mathematical principles, ie by definition. Nothing about the web 
follows from mathematics.

> > >  It's a matter
> > >of perspective. There aren't any constraints in the
> > >design of the Web that allow you to deduce a contradiction
> > >from saying "every document is on the Web".
> >
> > More important, I think, than the lack of a contradiction is a sense of
> > common understanding (which, also, is an act of faith...).
>
>Alas, it's true that a lot of folks think of the Web
>as HTTP+HTML. They speak of "the Web or email or ftp"
>when they should say "HTTP or email or ftp, all of which
>are part of the Web." The telephone system is also
>part of The Web, as is IRC etc.

The web uses the phone system, but it does not include it. I do 
actually speak on the phone from time to time.

>cf rough notes
>  http://www.w3.org/2001/01/rtriw44
>and running code
>  http://dev.w3.org/cvsweb/2001/telagent/
>
>I agree that this common understanding is somewhat lacking
>and important to achieve; I plan to spend considerable
>effort developing it over the next few years.
>But meanwhile, the 10 year history of the Web
>is evidence that this axiom is useful; can we agree that
>for the purposes of the RDF spec, every document is in the Web?

No, we cannot. I refuse to accept as an axiom something that I know 
to be false and, moreover, I know to be false because I can make it 
false in a few seconds by writing something with a pen on a piece of 
paper.

Pat Hayes

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Received on Wednesday, 20 June 2001 19:13:47 EDT

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