W3C home > Mailing lists > Public > www-rdf-logic@w3.org > June 2001

Re: Predicates and Arcs vs Triples RE: use/mention and reification: rdf:predicate/subject/object

From: Jonathan Borden <jborden@mediaone.net>
Date: Fri, 1 Jun 2001 08:30:34 -0400
Message-ID: <065001c0ea96$a81c8810$0a2e249b@nemc.org>
To: "pat hayes" <phayes@ai.uwf.edu>, "Graham Klyne" <GK@NineByNine.org>
Cc: <www-rdf-logic@w3.org>

Jonathan Borden
The Open Healthcare Group

----- Original Message -----
Graham Klyne wrote:

> I'll hazard an opinion that what you describe as genuine reification is
> handled in RDF by literals, without any built-in interpretation.  Thus, to
> distinguish between:
>     John says "The sky is blue"
> and
>     John says-that (the sky is blue)
> I think RDF aims to handle the latter, but not the former.  In the latter
> case, I think it is an RDF expression associated with John's utterance
> can be interpreted, not the utterance itself.  The utterance must be
> expressed (interpreted?) as RDF before it can be "understood" by an RDF
> processor.

To briefly summarize at least one killer problem with the current RDF

what we would _like_ to be able to say is:

<ex:says rdf:about="http://example.org/people#John">
        <ex:color rdf:about="http://example.org/things#sky"

(really we should be able to use qnames all around to say:


but that's a different issue)

but as statements are explicitly stated to be _facts_ per RDF M&S 1.0 we
can't say this without asserting that (color sky blue) is true, rather what
is needed is:

<ex:says rdf:about="http://example.org/people#John">


Now suppose I enter a statement to the effect that "everything John says is

The model _does not_ contain a mechanism to unreify the statement _as a
statement_ i.e. still does not contain the statement:

[:color :sky :blue]

so this property that statements are facts is not transitive i.e. facts are
not necessarily statements.

What then is the purpose of asserting that _statements are facts_ besides
requiring this cumbersone reification mechanism?

Since deciding whether a statement is _true_ must be computed regardless, it
is far better (IMHO) to use:

1) context/spaces
2) namespaces

as 'coloring' mechanisms to label semantically meaningful subgraphs (e.g.
asserting an entire context true, and assigning semantics to terms in the
rdf: and logic: etc. namespaces.

Received on Friday, 1 June 2001 08:47:31 UTC

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