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

Why? Re: rdf as a base for other languages

From: Jonathan Borden <jborden@mediaone.net>
Date: Fri, 1 Jun 2001 14:59:37 -0400
Message-ID: <070501c0eacd$01db2bf0$0a2e249b@nemc.org>
To: <www-rdf-logic@w3.org>, "Sandro Hawke" <sandro@w3.org>
Sandro Hawke wrote:

> >> The only potential for confusion I see is that some people might want
> >> to jump from having a triple described (with ground facts) to assuming
> >> the described triple is true, but that seems clearly wrong.
> >
> >Calling something a "fact" implies that it is "true". You might try to
> >assert a falsehood but that would be false or inconsistent. To be
consistent
> >you must assert a fact, i.e. the fact _must be_ true. What am I clearly
> >missing?
>
> I don't understand where we're not understanding each other.

Probably because we are talking about reification. It is confusing (to me).

Perhaps I have misread you. When you say "having a triple described by
ground facts" do you mean that the ground facts are:

[#S1 rdf:type rdf:Statement]
[#S1 rdf:subject ex:foo]
[#S1 rdf:predicate ex:bar]
{#S1 rdf:object ex:baz]

and not:
[ex:foo ex:bar ex:baz]

?

I guess what I am getting at is that the only need to introduce these
mechanics (using 4 triples to describe 1) is that triples themselves are
being _defined_ as facts. So when you want to _describe_ a triple without
declaring it as a fact, you need to introduce _4 other facts_.

On the other hand if a triple:

[ex:foo ex:bar ex:baz] is simply a triple and no state of 'truth' or
assertion is assigned to it by the fact that it exists as a member of the
set of Statements, then this triple needs no description by 4 other triples.

>
> For example, here are 7 facts:
>   1.  I can imagine a condition, X.
>   2.  X can be expressed accurately as English sentence Y.
>   3.  Y has four words.
>   4.  The first word of Y is "the".
>   5.  The second word of Y is "sun".
>   6.  The third word of Y is "is".
>   7.  The fourth word of Y is "shining".
>
> Now I'm not exactly sure which of X and Y might be best called a
> "condition", "state", "statement", "declartion", "sentence",
> "situation", etc, etc. but using only true ground facts I have
> essentially communicated X and Y to you without asserting them.
>
> If you take everything I say as true and I add an 8th fact: "X is
> true" or "X is a fact" then you are licensed to infer that the sun is
> shining.
>
> If instead I add an 8th fact: "X is not true" then I have made no
> contradiction; I have actually made a reasonable and useful statement,
> licensing you to infer that the sun is, in fact, not shining.
>
> Do you have any problem with this approach, beyond style?

My problem with this approach is this:

In order to decide the truth of any statement "X" I cannot simply test
whether it is or is not a direct member of the set of Statements. If it is
not a member, "X" might still be true, because it is inferred from the other
statements as you describe.

Indeed assessing the truth of Y is quite difficult given the way you have
expressed this "knowledge"

So why say that statements are true just because they are members of this
set? Doing so does not eliminate the need to perform inferencing, and at the
cost that statements that are refered to need be expressed in a cumbersome
and confusing manner.

What do you indend to do with your set of facts? Does expressing these facts
in the manner you have done above facilitate accomplishing your goal?

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).

-Jonathan
Received on Friday, 1 June 2001 15:16:58 GMT

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