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Re: use/mention and reification

From: Dan Brickley <danbri@w3.org>
Date: Tue, 22 Jan 2002 10:42:08 -0500 (EST)
To: Jan Grant <Jan.Grant@bristol.ac.uk>
cc: Dan Connolly <connolly@w3.org>, RDFCore Working Group <w3c-rdfcore-wg@w3.org>
Message-ID: <Pine.LNX.4.30.0201220947120.29151-100000@tux.w3.org>
On Tue, 22 Jan 2002, Jan Grant wrote:

> On 21 Jan 2002, Dan Connolly wrote:
>
> > On Mon, 2002-01-21 at 04:06, Jan Grant wrote:
> > > On 18 Jan 2002, Dan Connolly wrote:
> > [...]
> > > I still don't understand why you can't pronounce
> > >
> > > 	<sentence> <rdf:Subject> <mary> .
> > >
> > > as "the sentence has a subject whose referent is (the person) Mary" -
> > > ie, if you just change your intuition about what rdf:Subject "means"
> > > does this go away?
> >
> > Well, yes. That is: it becomes completely useless to me.
>
> Well, I've (re-)read the thread you pointed at, and I'm at a loss. My
> intuitive reaction was that your need for quoting was an artifact of the
> KIF mechanisms you were using, but I'm not a KIF guru by a long chalk.
> Is there something else you can point me at which would enlighten me as
> to what you're actually trying to _do_ with reification?

I'll leave that for DanC to expand on. If my own goals for using rdf
reification are still obscure, I could expand on those too, elsewhere.
Colloquially, my goal is 'carrying RDF through RDF' while preserving
information on the specific URIs used in the enclosed/encoded RDF.

> I'm trying to figure out what the fundamental assumptions are that don't
> mesh.

Good plan.

> Danbri seems to be talking about a reification along the lines of:
>
> 	jan said "may had a little lamb"


Can we try a variation on this example instead, please? For those who get
the cultural reference ('clark kent' and 'superman' being two names for
the same thing, although Lois doesn't know this) it seems to draw out the
issues nicely. Borrowing from
 http://plato.stanford.edu/entries/prop-attitude-reports/index.html#amb :

	lois accepts "Superman is Strong"
	(lois does not accept "Clark Kent is Strong")

> where "said" means, "emitted the following symbols"*, where I prefer
(we could fuss over quite what 'emitted the following symbols' amounts to,
but its good enough for me. i'm using 'accepts' instead of 'said' but the
example still works, I think)

> 	jan said that mary had a little lamb

	lois accepts Superman is Strong
	(lois does not accept Clark Kent is Strong)

[substituting co-referring terms...]

	lois accepts Clark Kent is Strong
	(lois does not accept Superman is Strong)

(btw if my use of 'not' distracts, ignore the parenthesised 2nd sentences).

> (this distinction doesn't render very well in english, I'm afraid) where

Indeed. This (or a close-enough-for-us) distinction gets called 'De Re /
De Dicto', presumably to emphasis the inadequacy of English... ;-)

See http://plato.stanford.edu/entries/prop-attitude-reports/dere.html
http://plato.stanford.edu/entries/prop-attitude-reports/index.html#amb
and http://plato.stanford.edu/entries/prop-attitude-reports/index.html
...for some discussion of the distinction and associated (and well
documented) puzzles. This is not a new problem.

> I'm attempting to reflect meaning, not the symbols used to convey that
> meaning.

(the former is 'de re', the latter 'de dicto', as I understand it).

So I'm claiming that more often the 'meaning not symbols' (de re) approach
to rdf reification results in unacceptable information loss, and creates
opportunities for confusion and miscommunication. See Lois example for details.
If the example doesn't prove contentious, we could roll it up as a test
case perhaps?

> These two points of view don't appear to be reconcilable.

Both forms have their uses. But we can go from a de dicto ascription to de
re safely (I think...[1]), but not back the other way. Given that
asymetry, chosing the preserve-the-symbols approach seems pretty
attractive.

> jan

dan


[1] we'd need additional assumptions, eg. of rationality of the
agent the content was being ascribed to.

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Received on Tuesday, 22 January 2002 12:41:30 EST

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