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Re: Semantics101, 2 and 3

From: Adrian Walker <adrianw@snet.net>
Date: Tue, 14 Jun 2005 12:05:20 -0400
Message-Id: <>
To: "Massimo Marchiori" <massimo@w3.org>
Cc: public-rule-workshop-discuss@w3.org, <harold.boley@nrc-cnrc.gc.ca>, tim.glover@bt.com, francois.bry@ifi.lmu.de

Hi Massimo --

Thanks for your thoughtful comments, below.

I like your 3-dimensional version of the layer cake diagram, but perhaps 
there is a growing consensus that the "people axis" is not in fact 
orthogonal to the rest.  Instead, the icing at the top of the 2-d layer 
cake should be an 
authorability-understandability-explainability-accountability block.  That 
would serve to emphasize that semantics102-3 design decisions in the top 
layers are interdependent.

These days, the Rules and OWL blocks in the layer cake are at the same 
level.  So, Rules can reach for data in the lower levels directly without 
consulting OWL.  What would be the reasons for rules on top of OWL?

I look forward to the mystery paper you mention from the usual suspects.

                                 Cheers,  -- Adrian


Adrian Walker
Reengineering LLC
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CT 06011-1412 USA

Phone: USA 860 583 9677
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At 05:14 PM 6/13/2005 -0400, you wrote:

> >  There are at least three kinds of semantics to consider:
> >
> >    101 --  tagging data and predicates with their real world types, as in
> > xml or rdf
> >
> >    102 -- model theory based semantics that say what *should* be deducible
> > from
> >              a collection of rules and facts
> >
> >    103 -- executable English sentences that document what we mean by our
> > predicates
> >
> >  I think we all pretty much understand the 101 part.
>Adrian, I understand it if that means types are needed (a la thesis
>9, "language engineering", of the Ten Theses paper [TT]), and it
>doesn't mean at all it's an easy thing to do... xml and rdf type
>systems are two quite different things by now... ;)
> >
> >  For 102, there is the question of *which* semantics.  The leading
> > candidates would appear to be (a) stratified range-restricted datalog
> > with negation [1], or (b) the well-founded semantics [2].  Note that (a)
> > is two-valued -- true or false -- while (b) is three-valued -- true,
> > false or unknown.  There are many successor papers to each of [1] and
> > [2].
>Saying these two are the leading candidates looks like a bold
>assumption... ;) I'd say these are two candidates, as many other
>people have their favourites that differ from those two.
>Or, well, I would *bet* many other people have their favourites ;)
>There's also the problem of where this rule language
>is going to sit: if on top of OWL, or aside, which also has
>deep implications on the semantics. There's a very nice paper
>by some "usual suspects", that will be shortly published (so for now,
>sorry, no pointer until that gets accepted or the authors want
>to post it earlier), nicely showing the dangers of underestimating
>the "on top of OWL" issue.
>And some other people have also doubts this different views
>might even be reconciled, whereas another view could be possible,
>the "diversity approach" (cf. thesis 1 of the Ten Theses paper,
>[TT] ).
> >  The need for semantics103 can be seen by reading the jena-dev and other
> > SW-related lists.  There, one daily sees smart people getting thoroughly
> > confused about the meanings of RDF and OWL constructs and reasoning
> > processes when translated into English.
> >
> >  In our work, we have fielded an online system [3] that meets the 103 need
> > without getting deep into NL research.
>I completely agree: even more, one doesn't need to go as long
>as looking into jena-dev, as this issue in the sweb came up much earlier,
>cf. Metalog (http://www.w3.org/RDF/Metalog/ ) with the PNL layer
>(http://www.w3.org/RDF/Metalog/docs/pnl.html ). And much earlier in
>the industry side too: as you know and as you substantiated with
>your own implementation, it's common pratice there to be much more careful
>of the "people axis" (http://www.w3.org/RDF/Metalog/docs/sw-easy.html)
>and provide for some sort of controlled english/pnl interface for the
>customers; in fact, the vast majority of commercial rule engines
>nowadays offers such a layer.
>Not to underestimate also the companion "visual layer", cf. for
>instance visXcerpt
>(http://www.pms.ifi.lmu.de/rewerse-wgi4/software/visXcerpt ),
>which is a nice analogous approach to climb up the People axis,
>this time using the visual layer instead of the verbal one.
>Both of these twin aspects are summarized into thesis 10
>(Visual and Verbal rendering) in the Ten Theses paper [TT].
>Relatedly, the european Network of Excellence on web reasoning
>REWERSE (www.rewerse.net) is bringing forth these issues with quite
>some strength in its overall view of technologies.
> > However, the system depends on
> > having a firm basis at the Semantics102 level.  Thus, this is more than
> > 'syntatic sugar'  [4].  For example, a two-valued closed world
> > semantics102 can support, at the semantics103 English level, an open
> > world flavored predicate such as &quot;so far as is known at the moment,
> > flight 678 is on time&quot;.
>Yes, absolutely, the axes are not disjoint but dependant on each
>other. And, yes, the verbal/visual layer is not at all "second class",
>but ought to be first class, for the implications it brings with it
>(and ought to be an explicit SHOULD/MUST in a list of requirements).
>[TT] Ten Theses on Logic Languages for the Semantic Web
>      http://www.w3.org/2004/12/rules-ws/paper/15/
Received on Tuesday, 14 June 2005 16:05:49 UTC

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