From: Michael Kifer <kifer@cs.sunysb.edu>

Date: Sat, 27 Aug 2005 16:22:01 -0400

To: jos.deroo@agfa.com

Cc: sandro@w3.org, public-rule-workshop-discuss@w3.org

Message-Id: <20050827202201.79111CB5D3@kiferserv.kiferhome.com>

Date: Sat, 27 Aug 2005 16:22:01 -0400

To: jos.deroo@agfa.com

Cc: sandro@w3.org, public-rule-workshop-discuss@w3.org

Message-Id: <20050827202201.79111CB5D3@kiferserv.kiferhome.com>

> > I was also thinking like that Sandro, but Michael argued and argued > and I was not able anymore to counterargue.. Looking back at > http://lists.w3.org/Archives/Public/public-rule-workshop-discuss/2005Aug/0090.html > 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? Yes, because you have a luxury of a "logic" language without the normal logical attributes: a semantics and a proof procedure that is at least sound with respect to the semantics. I was trying to make a logical sense out of it. The fact that your engine doesn't say that fred's hair is red is just a property of your engine, which does what it does. Since N3 has no semantics, I can't say whether the answer is correct or not. If I were to give a reasonable logical semantics to N3, I would have said that the formulas sitting at <uri-of-document> are asserted and true. The log:semantics predicate is a meta-logical means of reflecting (reifying) those formulas; it makes lists out of the true formulas sitting at <uri-of-document>. There is a long way to go from here to a reasonable semantics, but it is a start. When I was "arguing and arguing" I had this severely under-developed semantics in mind. At least, it gave me a way to think of what was going on in logical terms. In the absence of ANY semantics of this kind, our entire discussion about monotonicity is meaningless. --michael > 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 > De_Roo/AMDUS/MOR/Agfa-NV/BE/BAYER) > 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 > formula. > > 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 20:22:10 UTC

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