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Re: resources and URIs

From: Tim Berners-Lee <timbl@w3.org>
Date: Mon, 21 Jul 2003 08:41:52 -0400
Cc: pat hayes <phayes@ihmc.us>, www-tag@w3.org
To: Graham Klyne <GK@ninebynine.org>
Message-Id: <B4030B17-BB78-11D7-AF3A-000393914268@w3.org>

On Sunday, Jul 20, 2003, at 03:26 US/Eastern, Graham Klyne wrote:

> Tim,
>
> Your message below seems closer to my understanding, except your 
> comment about "assumption of a single interpretation" -- maybe this is 
> just a terminological slip, but if we're talking about interpretations 
> in a model theoretic sense, I think it's important to not try and 
> claim any *single* interpretation.

I'm not claiming that there is any single *well defined* interpretation.
What I do, as you do, is point out that under certain rules, the 
deductions (and action)  your agent makes are indistinguishable from 
those of an agent who does assume a single interpretation.

> [Background terminology check:  An "interpretation" arbitrarily 
> assigns a single value from some domain to each of a set of names.  A 
> "denotation" of a name is the value assigned to that name by some 
> given interpretation.  Thus, for a given name there are multiple 
> denotations corresponding to each interpretation that mentions the 
> name.]

Absolutely. ("arbitrarily"?.  An agent considers interpretations which 
are consistent with the data.
So when I see and chose to believe
   <#pat> contact:mailbox <mailto:phayes@ihmc.us>.
I immediately rule out the interpretation in which  `<#pat> denotes 
China, `contact:mailbox` denotes geographical inclusion, and 
<mailto:phayes@ihmc.us> denotes France.
To take an arbitrary example.).


> So, picking up your line of consistency and experimentation, if an 
> "identity" is derived from (is the set of denotations according to) a 
> set of interpretations that are consistent to some level of 
> observation, we always have the possibility that additional 
> observations will detect inconsistencies, hence fragment the identity 
> into several distinct "sub-identities", each derived from a subset of 
> the interpretations of the original.  In this sense an "ideal" 
> identity (e.g. in the sense intuitively/informally used for URIs) 
> might be derived from the limit of some set of consistent 
> interpretations as the number of observations considered tends to an 
> infinitude of all possible observations.  That is, we can never know 
> the identity completely, but may know it well enough for any given 
> purpose.

Yes.

(I am reminded of a playground argument, "How do I know you don't see 
red as what I see as blue.  You would call it blue, because everything 
I see as blue you would say was blue when in fact it would be red."  
While that which is "really" denoted can never be itself measured, it 
doesn't make any difference)

> (In saying this, I'm trying to paraphrase in non-mathematical terms 
> the way that definitions of limits and continuity are used in 
> differential calculus.)

> (Reviewing what I wrote here, it seems that a corollary is that any 
> identity corresponds to (or may in general correspond to) an infinite 
> number of possible denotations.  I think that underscores the point 
> about not assuming a single interpretation.)
>

For me what underscores the need for being aware of possible 
differences in denotations is the actual possibility that new 
information may turn up distinguishing two things.

However the danger of being too aware off it is that we spend too much 
time worrying about it, like the kids worrying about what people really 
see.

Another danger is that we loose the *intent* that URIs should be used 
to represent globally unique things.  For example, if this talk of 
multiple interpretation allows sloppiness in modeling for example 
peoples' home pages, people's mailboxes, and people themselves in the 
knowledge representation, then automated inference is doomed.

tim

> #g
> --

Received on Monday, 21 July 2003 17:55:48 UTC

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