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Re: log:notIncludes (conclusion?)

From: <jos.deroo@agfa.com>
Date: Sat, 27 Aug 2005 21:28:25 +0200
To: sandro@w3.org
Cc: Michael Kifer <kifer@cs.sunysb.edu>, public-rule-workshop-discuss@w3.org, public-rule-workshop-discuss-request@w3.org
Message-ID: <OFA276CAD7.45A1DE29-ONC125706A.00686EE3-C125706A.006AF068@agfa.com>

I was also thinking like that Sandro, but Michael argued and argued
and I was not able anymore to counterargue.. Looking back at
Michael, your set A is

1.   { <uri-of-document> log:semantics ?F.
      ?F log:notIncludes { sky color blue } }
                   => { thisTest a Pass }.

2.   fred hairColor red.

but what exactly is the logical connective between 1 and 2?
I'm pretty sure it is *not* logical AND: the triple in 2
(which lives at <uri-of-document>) is *not* asserted in my
engine whereas the triples/rules in graph 1. are asserted.
I mean, if you ask cwm or euler to prove  fred hairColor red
you would simply get no proof, as that triple is not asserted.
If it is not logical AND then how can one talk about adding?
Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/

Sandro Hawke <sandro@w3.org>
Sent by: public-rule-workshop-discuss-request@w3.org
27/08/2005 20:51

        To:     Michael Kifer <kifer@cs.sunysb.edu>
        cc:     public-rule-workshop-discuss@w3.org, (bcc: Jos 
        Subject:        Re: log:notIncludes (conclusion?)

> I think the key is that semantics(+URL,-Formula) predicate and the fact
> that you are leaving out of the picture the actual formulas that are
> sitting at URL. The formula that you are getting using semantics/2 is 
(as I
> understand) a list of terms that reify logical statements.
> So, you have
> formulas sitting at URL  (*)
> the built-in semantics(URL,Formula)
> and then you have something like
>     Formula notIncludes somelist
> So, adding a new formula to the set (*) can change the list Formula
> and invalidate a previously true statement of the form
> Formula notIncludes somelist.

Yes.  I think we're understanding each other very well, now.

> This is nonmonotonic.

I'm not sure I know the right words for this, but that stuff sitting
at that URL is considered immutable within one inference run.  cwm
makes no attempt to read it more than once; any change in it would go
along with an overall change in the state of the world.  A
long-running N3-based agent would have to start everything over each
delta-t (or cleverly act like it did).  Each time something observable
about the universe changes, we're talking about a new set of models
and interpretations.

Going back to the definition of monotonicity you and DanC were using
[1], the stuff sitting at that URL isn't part of A or B.  Nothing is
entailed by that stuff at the URL.  To be slightly silly, adding a
formula to it is no more relevant to the notion of monotonicity than
is adding characters to the end of some constant symbol in an FOL

Now, am I sounding confused again or like this is a sensible design
(even if not the one you might chose)....? 

      -- sandro

[1] http://lists.w3.org/Archives/Public/public-rule-workshop-discuss/2005Aug/0072
Received on Saturday, 27 August 2005 19:28:42 UTC

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