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RE: URI for language identifiers

From: <Patrick.Stickler@nokia.com>
Date: Wed, 2 Apr 2003 11:07:47 +0300
Message-ID: <A03E60B17132A84F9B4BB5EEDE57957B5FBB5E@trebe006.europe.nokia.com>
To: <pfps@research.bell-labs.com>
Cc: <miles@milessabin.com>, <www-rdf-interest@w3.org>



> -----Original Message-----
> From: ext Peter F. Patel-Schneider 
> [mailto:pfps@research.bell-labs.com]
> Sent: 01 April, 2003 17:20
> To: Stickler Patrick (NMP/Tampere)
> Cc: miles@milessabin.com; www-rdf-interest@w3.org
> Subject: Re: URI for language identifiers
> 
> 
> From: <Patrick.Stickler@nokia.com>
> Subject: RE: URI for language identifiers
> Date: Tue, 1 Apr 2003 16:32:09 +0300
> 
> > > -----Original Message-----
> > > From: ext Miles Sabin [mailto:miles@milessabin.com]
> > > Sent: 01 April, 2003 16:10
> > > To: www-rdf-interest@w3.org
> > > Subject: Re: URI for language identifiers
> > > 
> > > 
> > > 
> > > Patrick Stickler wrote,
> > > > *How* or *where* a given URI is used does not affect its
> > > > authoritative meaning. Usage can only reflect the presumptions
> > > > of the user, but that does not usurp the authority fo the owner,
> > > > and may very well result in disagreement or ambiguity.
> > > 
> > > I'm sorry, but this is just wrong.
> > > 
> > > Other than intrinsic network and DNS semantics, there 
> isn't currently 
> > > any notion of an authority for a URI which has semantic 
> relevance to 
> > > RDF.
> > 
> > Either you have not understood what I was saying, or you 
> are simply wrong
> > (or both ;-)
> > 
> > The denotation of a given URI is that which the owner of that URI
> > specifies. Period.
> 
> Hmm.  Where does this come from?  Can you provide anything 
> besides your own
> gut feeling for this?

Can you provide anything to refute it other than your own gut
feeling for this?

However:

From http://www.ietf.org/rfc/rfc2396.txt
[
   3.2. Authority Component

   Many URI schemes include a top hierarchical element for a naming
   authority, such that the namespace defined by the remainder of the
   URI is governed by that authority.  This authority component is
   typically defined by an Internet-based server or a scheme-specific
   registry of naming authorities.
]

where a "naming authority" is that agency which (either directly or 
indirectly) mints a URI and defines its denotation -- i.e. which names 
a resource by a URI.

That authority either equates to, or may designate, the creator (owner) 
of a given URI and it is the creator which specifies what the URI denotes.

True, the actual agency is indirectly identified by the naming authority
component of the URI scheme, being e.g. the owner of a given domain name,
IP address, registry domain, etc. but the identity of the agency is
clearly determinable.

And even if the determination of ownership for a given URI may take
some investigation -- for any given user, it should be clear when
they *don't* own a given URI, and thus should look to the owner for
what it denotes. 

This issue has been explored at length by the RDF Core WG and (while
not to be included in the final specs, but in a separate publication)
the discussion regarding the meaning of URIs authored by the WG is
illustrative of the shared view of many members of the SW community:

From http://www.w3.org/TR/rdf-concepts/#section-Social:
[
   4.3 Authoritative Definition of Terms

   The social conventions surrounding use of RDF assume that any RDF URI 
   reference gains its meaning from some defining individual, organization or 
   context. This applies most notably to RDF predicate URI references. 

   These social conventions are rooted in the URI specification [URI] and 
   registration procedures [URI-REG]. A URI scheme registration refers to a 
   specification of the detailed syntax and interpretation for that scheme, 
   from which the defining authority for a given URI may be deduced. In the 
   case of http: URIs, the defining specification is the HTTP protocol 
   specification [HTTP], which specifies how to use the HTTP protocol to obtain 
   a resource representation from the host named in the URI; thus, the owner of 
   the indicated DNS domain controls (observable aspects of) the URI's meaning. 

   Thus, the choice of terms used in published RDF is significant in determining 
   its meaning, through reference to definitions asserted by the defining 
   authorities for those terms. 
]

Thus, the views that I have been expressing here are both reflected in 
the URI specs as well as reflect common opinion in the SW community.


> > And any disagreement about the denotation of a given URI utimately
> > must be resolved by the owner of that URI.
> 
> Hmm.  Where does the notion of the (unique) owner for (every) URI come
> from?   For example, who is the owner of
> 	http://www.bellllabs.com/user/pfps/#me

I couldn't say. Though to find out, I'd first contact the owner of 
the domain www.belllabs.com, and I'd expect I'd likely be told that
the sub-webspace http://www.belllabs.com/user/pfps/ was controlled
by you, and that all URIs grounded in that sub-webspace are under
your ownership. Therefore, you are probably the owner of the URI
http://www.belllabs.com/user/pfps/#me and if I wanted an authoritative
definition of what that URI denotes, I'd ask you specifically.

Is that really so difficult?

> Even if there is an owner of a URI, how does that owner 
> determine what a
> URI means?  

The issue is not *how* the denotation of a given URI is defined,
but *who* has the right to define it.

> Even if there is some platonic notion of the 
> ultimate meaning
> of a URI, how is that meaning conveyed to RDF (or DAML+OIL, or OWL, or
> LBase, or any other formal system in the Web)?

You are now diverging to an entirely different issue.

The three key points of this thread are:

1. URIs should have unambiguous, consistent, global, and immutable denotation.
2. Each URI has a specific owner, who has the right to say what it denotes.
3. Statements made by owner of a resource can be considered to have special 
   sigificance/authority over statements made by 3rd parties.

How the denotation of a given URI is defined, or how the semantics of the
resource denoted are defined, are outside the scope of this particular
discussion.

They're important issues in their own right, of course. Feel free to
start a separate thread to discuss them.

> > If I mint a URI and say it denotes the city of Paris, France. And
> > you come along and use it to denote the city of Paris, Mississippi,
> > then you are wrong and I am right, because it's *my* URI. 
> 
> How is it your URI?

Because I created it. Is that really so hard to understand?

> > It's as
> > simple as that. 
> 
> This is not simple, it is, instead, extraordinarily complex.

No. I think you simply want it to be complex. Or perhaps are
not able to dissect a number of disjunct issues and address
each individually. The issue of URI ownership and denotation
is very simple.

> For example, suppose DC Comics mints a URI reference, 
> 	http://www.dccomics.com/#clarkkent
> what exactly does this denote?  

Whatever DC Comics *says* it denotes. They created it,
so they get to say what it means. Simple.

If that denotation doesn't work for you, then don't use it.

> Can I use this as a synonym for
> 	http://www.dccomics.com/#superman

Probably not, since the names carry "perspective" in addition to
denotation of some entity. But you digress.

Again, you are diverging into yet another issue that is completely
disjunct from the issue being discussed.

Whether or not two different names which denote the same entity can
be used interchangably, as they may reflect distinct "perspectives" 
of that entity (such as "Morning Star" and "Evening Star" both denoting
the planet Venus) that has nothing whatsoever to do with whether a
given URI has ownership and whether the owner has the ultimate right
to say what it denotes.

Again, if you wish to explore other issues, feel free to start a
new thread.

> > The owner of a URI gets to say what it denotes and
> > if you don't agree, then don't use that URI. Use of someone elses
> > URI is an implicit agreement about what the owner says it denotes
> > (leaving aside cases of misunderstanding, etc.)
> 
> So how then can I utilize URI references such as 
> 	http://www.whitehouse.gov/#43
> I may want to use this well-known URI as a common source of 
> URI references
> for the U. S. presidents, so that I can communicate with other people.
> However, I, like Michael Moore, may disagree with the denotation that
> www.whitehouse.gov gives to this particular URI reference.  

Tough. Too bad. If you don't agree with, or can't use the authoritative
denotation, then you'll have to find some other names to use.

Actually, I don't see how you can "disagree" with what the creator
of a URI says it denotes, since you have no authority to say otherwise.

You may disagree with some statement made about the *resource* denoted
by a give URI, but you don't have any basis for disagreeing with 
the denotation specified by the creator of the URI, as the creator of
a URI has the sole right to say what it denotes.

> If I have to
> use the denotation given by www.whitehouse.gov, then I have 
> no way of even
> expressing disagreement with that denotation.

Correct. If you use that URI, you implicitly agree with its specified
denotation. If you don't want to talk about what that URI is specified
to denote, then don't use that URI. Pretty simple really.

> > Likewise, if I have a URI that denotes a document that I wrote and
> > of which I am the owner, and I make a statement that e.g. it has
> > 4293 characters of textual content in it and you say it has only
> > 1882 characters of textual content in it, then my assertion bears
> > an authority that yours does not. True, it may very well be that you
> > are correct and I might be incorrect, but that doesn't in any way
> > change the fact that assertions about a resource made by the 
> > owner of the resource bear special authority over assertions made
> > by third parties.
> 
> Huh?  How?  Why?  What good does this do?

Well, to take one simple practical example, perhaps a manufacturer of
a product has published some information about that product, and some
trade publication has also published similar information about that
product. Knowing who has said what may be very important in choosing
what information one wishes to trust over the other. It may be that
one trusts the trade publication more than the manufacturer. Or one
may be aware of common errors made by that publication and wishes to
let knowledge from the manufacturer take precidence in the case of
a disagreement.

> > > Ironically, your claiming that there is such an authority is 
> > > an example 
> > > of a local ascription of meaning based on idiosyncratic use ;-)
> > 
> > I don't see that. I think you should re-read my post. Perhaps you
> > missed what I was saying...
> 
> I don't think so.  I think that Mile's comments are exactly 
> correct.  

Then it appears that you're both wrong ;-)

> All
> that there is in your post is one person's feelings as to how URI
> references are to denote.  Any other person could have a 
> different view of
> how URI references are to denote, and that other view would 
> have just as
> much validity as your view.

Sorry, but I believe that my view is born out by the specs, as outlined
above. I also belive that my view is the most predominant view in the
real world, both for developers as well as common users.

I also challenge both you and Miles to point to any normative content
in any relevant spec which suggests that individuals can mint URIs
using naming authorities they have no ownership or rights to, or that
the denotation of a URI specified by the creator of a URI can be 
questioned by any other party. Good luck.

> For example, here is a view that I happen to subscribe to
> 
> 	In any formal system, such as RDF, the denotation of a name
> 	(including URI references as a special case) is left 
> unspecified.

*In* RDF, yes, but not in the larger context of where and how that
formal system is used.

> 	Statements in the formal system, including RDF statements, serve
> 	only as constraints on that denotation.  

But not the *only* constraints on that denotation. It is presumed (in
fact IMO required) that there be system-external constraints on the
denotations of the names (URIs) used as atomic elements of that system.

RDF does not happen "in a vacuum". 

> Any agent (including
> 	people) choose to believe certain statements, and thus 
> every agent
> 	can potentially have a different view of the denotation of any
> 	particular name.

They *may*. But differing views in the *denotation* of URIs represents
a breakdown in the system. RDF presumes (even if it can't garuntee)
that URIs have globaly consistent, unambiguous, and immutable denotation.

RDF is *not* like natural language. RDF is intended to be much more
precise, as are all formal languages, while still tolerating a certain
degree of noise. Ambiguity and conflicting statements, even if tolerable
to a certain degree, are nonetheless undesirable and detrimental to the
optimal performance of that system, and therefore should be minimized
as much as possible.

> For contrast here is another view, that might be closer to your view
> 
> 	There is some ultimate, timeless reality.  The 
> denotation of every
> 	possible name is fixed and unchangeable in this reality.  

Or rather, 

   There is a formal system for which the names in that system are
   presumed to have unambiguous, consistent, immutable interpretation.

I don't see how the semantic web can offer any utility if it doesn't
correspond to such a formal system.

> This second view appears to be very nice, but there are quite 
> a number of
> problems in it, including how to provide a denotation of
> 	http://www.whitehouse.gov/#46
> and
> 	http://www.dccomics.com/#clarkkent

I see no problems with the denotation of these URIs. They denote precisely
what the creators of those URIs say they denote. If you don't want to 
talk about the particular resources the owners say they denote, then don't
use those URIs. It's as simple as that. You have *no* authority or basis
to disagree with the denotation specified by the creator of a URI. Tough.

> as well as how to deal with agents whose connection to this ultimate
> reality is incomplete or incorrect.

This is yet another issue, disjunct with the issue being discussed. Feel
free to start another thread to explore it.

Patrick

--
Patrick Stickler, Nokia/Finland, (+358 40) 801 9690, patrick.stickler@nokia.com
 
Received on Wednesday, 2 April 2003 03:09:56 GMT

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