W3C home > Mailing lists > Public > uri@w3.org > May 2003

RE: exploring ambiguity via the "something-which-has" URI scheme

From: Graham Klyne <GK@ninebynine.org>
Date: Wed, 07 May 2003 10:56:27 +0100
Message-Id: <5.1.0.14.2.20030507095908.025f7008@127.0.0.1>
To: <Patrick.Stickler@nokia.com>, <sandro@w3.org>
Cc: <uri@w3.org>, <phayes@ai.uwf.edu>

[Nothing of relevance to RFC2396bis herein]

At 11:47 07/05/2003 +0300, Patrick.Stickler@nokia.com wrote:
>I think that Pat and I actually are in more agreement about this
>than disagreement, and in fact the disagreement reflected above
>does not exist but arose out of my misuse of the terminology.
>
>My key point is that, for the SW (and not any application using RDF
>that is not considered to participate in the SW) all parties must
>agree upon denotations of a given URI which are compatible, even if
>not identical.

I think one of the continuing terminological problems is this (ab)use of 
"denotes".  In the context of RDF formal semantics, and model theoretic 
semantics generally (I think), the denotation of a URI is a feature of a 
particular interpretation, and different interpretations may assign 
different denotations.  This is irrespective of what we may intend a 
particular URI to mean or represent.

As for the intended meaning, I'm still trying to reconcile the ideas that 
we often think we know what a name is intended to represent, yet, as Pat 
says, language in general and RDF in particular does not provide any 
workable mechanism to fix a single meaning for a name.

I think there's an interesting parallel between the view of URIs as 
resource identifiers and formal semantics by model theory.  URIs are used 
to identify some (loosely specified) underlying concept of a resource that 
yields certain representations under certain circumstances.  Those 
representations are all we actually get to observe -- anything we may wish 
to know about a resource must be elicited in terms of such 
representations.   Model theoretic semantics likewise does not fix the 
exact meaning (denotation) of a name, but allows us to constrain its 
meaning by limiting interpretations to those which match certain statements 
we may choose to make.

What these seem to have in common is a limiting case.  The more we say 
about a resource, the more "closely" it may be constrained to some 
asymptote of meaning.  The more representations of a resource that we 
examine, the more we may learn about its "essential invariant 
characteristics".  But certaintly is elusive.

(Example:  let f(x) = sin(x)/x.  What is the value of f(0)?  We can't 
evaluate f(0) directly as it involves a division of zero by zero; but if we 
consider the region about x=0, then a credible argument can be sustained 
that f(0)=1, for x in radians, because Lim[x->0]f(x)=1.)

In the mathematics I've been exposed to, the concept of a limit is strongly 
related to some idea of a metric, so that we can talk in terms of relative 
closeness of pairs of values.    But there is no obvious metric for 
denotations of a resource.  (At this point I muse about things I don't 
really understand, such as the theoretical work underpinning aspects of 
denotational semantics of programming languages ala Scott/Strachey, also 
ideas of subsumption as appear in description logics...)

So can it make sense to think of the intended meaning of a name as a kind 
of region of meaning, bounded by those things we can observe or say about a 
resource?  Ambiguity remains, but within bounds that we trust will not 
affect the results we wish to achieve in using a name.  There is a kind of 
presumption here that one can make more observations, assert more 
constraints, to progressively constrain the nature of a resource in question.

#g


-------------------
Graham Klyne
<GK@NineByNine.org>
PGP: 0FAA 69FF C083 000B A2E9  A131 01B9 1C7A DBCA CB5E
Received on Wednesday, 7 May 2003 06:00:14 GMT

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