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RE: Why? Re: rdf as a base for other languages

From: Jonathan Borden <jborden@mediaone.net>
Date: Sat, 2 Jun 2001 12:09:17 -0400
To: <las@olin.edu>
Cc: <www-rdf-logic@w3.org>
Message-ID: <000901c0eb7e$600375a0$0201a8c0@ne.mediaone.net>
Lynn Andrea Stein wrote:

> Jonathan Borden wrote:
>
> > So why say that statements are true just because they are
> members of this
> > set? ...
>
> > To me, stating that each statement in Statements is a fact does
> not gain me
> > anything (in ease of inferencing) and costs me alot (of
> cumbersomeness and
> > confusion).
>
> Well, not "are true" and not "is a fact", but "is asserted by the
> document", at
> least, which may be the same as far as your concern goes.  Certainly the
> benefit (which is nonetheless present for some and in some
> applications) comes
> at a cost (for those who buy into inference as a given).

The cost, of course, is that when I say (stylized):

<if>
	<and>
		<hasHeadache rdf:about="las">severe</hasHeadache>
		<hasSpotOnMRI rdf:about="las">large</hasSpotOnMRI>
	</and>
	<and>
	  <isDiagnosis rdf:about="las">
	    <or>
		<benignBrainTumor/>
		<malignantBrainTumor/>
		<metastaticBrainTumor/>
	    </or>
	  </isDiagnosis>
	  <not>
		<isDiagnosis>
			<tensionHeadache/>
			<migraine/>
		</isDiagnosis>
	  </not>
	</and>
</if>


I really really don't mean to _assert_ that the diagnosis is one in that
particular list.

What I do wish to assert is the <if> expression. The problem with RDF as it
is currently defined (statement == triple == fact) is that I cannot assert
an expression created of multiple statements (i.e. a subgraph) apparently
without asserting each of the subgraphs within the subgraph.

What I do wish is to be able to 'draw a line' around a subgraph (or
expression take your pick) and assert _that_.

>
> I am under the impression that assertion by the document of statements
> contained within the document is a fundamental tenet of RDF and there's no
> changing it without dropping RDF.

I'm not sure who defines "fundamental tenets" except the community of people
who use RDF. That community is currently quite small, but a number of
people, myself included, wish to enlarge this community considerably. From
what I see, there are a few areas of RDF "hotspots" if you will that
generate 90% of the problems. The current mechanism of reification is
clearly one of those (e.g. see volume of email and absense of agreement
across wide spectrum of practitioners). The intention of RDF is clearly to
allow the representation of statements that are not asserted
(http://www.w3.org/TR/REC-rdf-syntax/#higherorder). I am suggesting that
this _mechanism_ can be changed without doing damage to the core ability of
RDF to represent edge labelled graphs.

> Assertion is *not* the same as
> truth of all
> statements or documents, but it is certainly something one could
> question if
> one were considering RDF or not RDF.  And I might take your
> approach in this
> respect if I were building a language from scratch.
>

I don't think we need to go that far. If RDF were considered 'done' and
stable, I'm not sure I see the need for the RDFCore WG activity (and note
that RDF Schema has never been finalized as a recommendation). Since these
remain on the table, in my view its better to fix things in one fell swoop,
rather than continue to argue about RDF reification for eternity.

I really really think this can be done without causing violence to what I
consider RDF's core ability: to represent the meaningful information in a
document in a reasonably simple fashion.

-Jonathan
Received on Saturday, 2 June 2001 12:10:41 GMT

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