Re: some notes

On Thu, 2003-09-25 at 22:22, pat hayes wrote:
[... I don't take issue with the first 2 points,
and I haven't read the ones after point 3...]

> 3. Unfortunately, RFC 2396 has conflated two rather different 
> relationships between a URI and a thing, viz. the 'identification' 
> sense in which a URI provides access to a source on a network, as 
> just outlined, and the 'denotes' or 'names' sense in which a URI is 
> simply a name which denotes something in the, or even in a, world. 

That's an interesting claim; you write lots of text after it,
none of which actually supports it.

> This in itself would not be so bad, in fact, if we recognized that 
> the first sense is a (very) special case of the second sense: after 
> all, network sources are things in the world, presumably, and can be 
> referred to.

quite.

>   But the RFC 2396 prose seems to be predicated on the 
> assumption that these two relationships are *identical*,

I don't believe so. Which prose?

>  which is 
> simply an error. It is a kind of colossal error, in fact, cosmic in 
> its metaphysical scale and consequences; it imports a surreal fantasy 
> into the very heart of the Web architectural theory.  Accepting it 
> has led a number of smart people into making fantastical, nonsensical 
> claims, such as that galaxies are 'on' the Web,

I see nothing nonsensical about saying that a URI identifies
a galaxy. I'm not sure what "on the Web" means, but recently
it seems to be limited to the case where URIs identify
network doodads. I'm not aware of anybody, smart or otherwise,
claiming that a galaxy is a network doodad.

>  or that the map is 
> the territory, or that resources have no identity criteria, or that 
> the act of typing a new a URI automagically brings a resource into 
> existence.
> 
> This conflation is seen in the strange uses to which this artificial 
> word "resource" has been put, where on the one hand, we are told that 
> resources are on a network,

some of them are.

>  are uniquely identified by URIs (in fact, 
> that it is a necessary truth that all URIs must identify a unique 
> resource) and that the URI provides access to the resource,

in some cases.

>  allowing 
> operations to be performed on it: and yet also, that a 'resource' can 
> be anything at all, including imaginary or Platonic entities, 
> galaxies far, far away and things that are too small to count or 
> identify.

in other cases.

>   This simply does not make any sense:

yes, it does if you're more careful with your quantifiers.

To say that *some* resources are network doodads
is not to say that *all* resources are network doodads,
i.e. it is not to say that galaxies are network doodads.

>  it doesn't make sense 
> to claim to provide access to perform operations on Julius Caesar or 
> the Whirlpool Galaxy.  What does make sense is that the first set of 
> conditions are appropriate and reasonable for the 
> URI-identifies-network-source notion, and the second claim makes 
> sense for the URI-denotes-entity notion. The craziness arises from 
> thinking these are the same and that the same 'resources' are 
> involved in both cases.

I don't see any craziness.


> I go over this stuff here (rather than the TAG group) because this 
> regrettable confusion has permeated these discussions.  Since (it is 
> claimed) a URI must identify a single resource - again, this does 
> make sense in one reading, but we are now going to move to the other 
> - that therefore all URIs must have a single *meaning*, and moreover 
> that this single meaning must be fixed globally in all uses of the 
> URI in all contexts.  This is bad enough: but this has taken even 
> crazier form in the idea that this must mean that all URIs must have 
> single denotation in all interpretations, a claim that is close to 
> being incoherent, rather than merely wrong.

I don't believe anyone holds the position that all URIs must
have a single denotation in all interpretations.

[...]

> So, the moral of this is, I claim, twofold: first, that we absolutely 
> must keep these two distinct ideas clear in our discussions - that 
> is, the network-maintained relationship between a URI and the 
> information source that it identifies, on the one hand, and the 
> semantic 'naming' relationship between a URI and whatever it might be 
> taken to denote, on the other.

The only moral I see is that we should be careful
with our quantifiers.


>  Intuitions which are appropriate to 
> one sense are quite inappropriate to the other.  Second, these two 
> senses are, prima facia, quite independent: there is no particular 
> necessary reason why a URI might not serve in both roles 
> independently. So when talking about 'meanings', we need to be 
> explicit about any relationships we might be presuming, or wanting to 
> insist on, between these two senses.
> 
> BTW, URN's are obviously names. They also obviously do not satisfy 
> the RFC 2396 prose: they do not, for example, provide access to the 
> things they name or allow operations to be performed on them. 

Yes, they do:

 A Trivial Convention for using HTTP in URN Resolution (RFC 2169)
 URI Resolution Services Necessary for URN Resolution (RFC 2483)
 and the list goes on, at
 http://www.ietf.org/html.charters/OLD/urn-charter.html
 
The software is less widely deployed, but
that's not a property of the strings, which provide
just as much access as http: URIs provide.

> (Wanting to subsume URNs and URLs under a common framework may have 
> been the source of this truly disastrous confusion, BTW.) They are 
> however a special case in that they seem to provide a uniquely 
> Webbish kind of naming authority. I will return to this point later.
> 
> 3. 

I think you meant 4 ;-)

-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/

Received on Friday, 26 September 2003 00:30:47 UTC