>Hi!
>
>Pat Hayes said:
>[...]
>>I am slightly concerned that this peculiar kink in the layer
>>cake has been put there deliberately to make it possible to do an
>>end-run around a unifying logic. Which when one takes into account
>>the whole point of "Unifying", would IMO be a pity.
>[...]
>
>I can understand that people insist on Semantic Web languages to have a
>formal, or even a model theoretic semantic. (01)
"even" ?? But never mind, let us proceed. (02)
>What I don't get is that you
>(and John F. Sowa in other emails) seem to insist that this must be classic,
>FOL like, monotonic semantic and that all formalisms with different
>semantics (or kinds of reasonings) have no place in the Semantic Web. (03)
You draw too rapid a conclusion. I don't think
that nonclassical logics have NO place on the
SWeb. But one has to draw a distinction between
'useful somewhere' and 'suitable as a basis for
global interoperability'. All of the Sweb
standards defined so far (RDF, OWL, SPARQL) are
intended for use at the 'top level' of the SWeb,
to be suitable for use for communication between
systems located anywhere on the Web, using data
which may come from many sources, be archived or
not, etc.. Under these assumptions one can make a
very good argument that the basic semantics of
such interoperation languages must be monotonic,
context-independent: because, in essence, the
context in which it was published is no longer
available at the point of use. See
http://www.ihmc.us:16080/users/phayes/IKL/GUIDE/GUIDE.html#LogicForInt
and
http://ontolog.cim3.net/file/resource/presentation/PatHayes_20061026/OntologyWorkshopSlides.html (04)
especially slides 4-6 (05)
>To me it seems obvious that these semantics cannot be the exclusive basis
>for reasoning on a global,open knowledge based system (06)
Not exclusive, but for the main basis, I think
one cannot really go much beyond classical
semantics, precisely because they are so weak.
All other semantics make some implicit assumption
which is not globally valid. (07)
>, because:
>
>1) These semantics do not consider (08)
True. But the fact that they do not consider
certain topics does not mean that those topics
are incompatible with them, or are ruled out of
consideration for ever. And one should not
usually seek to standardize topics which are
still the subject of active research discussion
and have no body of established practice to
appeal to. (09)
>quantitative aspects (e.g. 5000 locations
>state that a(mike), only 2 state that b(mike)), don't allow for closed world
>reasoning (010)
They ALLOW for it, but do not mandate it during
global information exchange, for the very good
reason that the Web is not a closed world. CW
reasoning is simply invalid when applied to the
entire Web. The unique name assumption is false;
failure is not negation; etc.. (011)
>, do not consider trust, require very strict global consistency.... (012)
Again, they do not REQUIRE global consistency, or
indeed even local consistency. They simply, as
classical semantics always do, give up when faced
with inconsistency. They do not deal adequately
with it, true: there is as yet no globally
acceptable standard way to deal with it. One has
to deal with each case on its merits. The fact
that the standards do not deal with these issues
is not a message that they are irrelevant or
prohibited, only that they are still the subject
of research and to some extent emergent future
practice. We will have to wait and see what
happens, before trying to impose a standard here. (013)
>Because of this they cannot reflect the intuitions and expectations of
>humans about what should be concluded from a set of statements as unordered
>and ungoverned as the web. (014)
I think you are muddling the chaotic state of the
Web with the idea that information on the Web
must be somehow faulty or inconsistent, or that
people use (or perhaps should use) a different
kind of reasoning when faced with a large messy
dataset. I don't think this is a valid
conclusion. Tim B-L has some interesting musings
on this topic, by the way. (015)
> Hence actual applications will in any case use
>other notions of truth and entailment (or come to conclusions that are not
>accepted by the users and probably not very useful).* (016)
What makes you assume that contexts and
uncertainty reasoning are excluded by a classical
semantics? (017)
>2) Should we really ever get reasoning semantic web agents, isn't it
>preposterous to assume that will rely exclusively on logical deduction? (018)
Perhaps not exclusively, but I think the main
basic inference mode will be deductive, yes. That
has certainly been the case so far in most
applications. Classical deduction can, with
current technology, be usefully applied to
datasets containing many millions of facts. (019)
>- Why
>not induction, abduction, analog reasoning, data mining, nlp, ir, simulation (020)
You are muddling together a host of unrelated
topics here. Induction and abduction are not even
logical forms of entailment, and are both
consistent with a classical notion of truth.
Analogical (aka metaphorical) reasoning turns out
in most application I have seen to be a
pattern-matching process on structures which
themselves have a classical semantics (and in
many cases are expressions in FOL.) Data mining
is a separate topic which is not required to be
nonclassical (we have used datamining software
with OWL, for example). NLP systems often use
deductive reasoning. And so on. Yes, Im sure all
these and more will be used by SWeb technologies
of one kind or another. None of that however is a
good reason for basing the global notations of
information exchange on anything more elaborate
than simple model theory. (021)
>... Doesn't this mean that in any case there will never be a complete
>mapping between the "proof" and the "logic" layer (as currently envisioned)?
>I also don't see how any kind of inference can be done on web scale without
>a large (essentially heuristic) information retrieval component trying to
>get the relevant statements (considering what we know about the complexity
>of inference algorithms) - again breaking the direct logic layer-proof layer
>mapping.
>
>my opinion in short: we don't have any semantics that covers everything that
>is needed (and I don't even see one at the horizon), hence we should not
>stifle innovation by insisting on one thats clearly inadequate for the task
>at hand. (022)
I agree with your premis, but draw a totally
different conclusion. As we MUST have an
interoperability standard to even get the SWeb
off the ground, we should choose one that
restricts innovation as little as possible: the
most bland, vanilla, uncontroversial basis that
everyone can accept and build on. What semantic
framework would you suggest be adopted as the
basis for SWeb information exchange? (023)
(BTW, I find your criticism kind of ironic, since
we have been the subject of torrents of criticism
for making the RDF and OWL-Full semantics too
'non-standard' by not basing it strictly on
textbook model theory.) (024)
Pat (025)
>
>
>cu
>
>valentin
>
>
>*: given the large amount of research into things like circumscription,
>uncertainty reasoning, rdf/dl+contexts etc. I was under the impression that
>this is a SW-community mainstream position.
>
>--
>email: zacharias@xxxxxx
>phone: +49-721-9654-806
>fax : +49-721-9654-807
>http://www.vzach.de/blog
>
>=======================================================================
>FZI Forschungszentrum Informatik an der Universität Karlsruhe (TH)
>Haid-und-Neu-Str. 10-14, 76131 Deutschland, http://www.fzi.de
>SdbR, Az: 14-0563.1 Regierungspräsidium Karlsruhe
>Vorstand: Rüdiger Dillmann, Michael Flor, Jivka Ovtcharova, Rudi Studer
>Vorsitzender des Kuratoriums: Ministerialdirigent Günther Leßnerkraus
>=======================================================================
>
>> -----Ursprüngliche Nachricht-----
>> Von: semantic-web-request@xxxxxx [mailto:semantic-web-request@xxxxxx]
>> Im Auftrag von Pat Hayes
>> Gesendet: Dienstag, 31. Juli 2007 17:20
>> An: John F. Sowa
>> Cc: [ontolog-forum]; Ivan Herman; Juan Sequeda; SW-forum list;
>> semantic_web@xxxxxxxxxxxxxxxx
>> Betreff: Re: [ontolog-forum] Current Semantic Web Layer Cake
>>
>>
>> >Pat,
>> >
>> >I agree that the proof box is misplaced, but I think
> > >that the major problem is that the logic box is not
>> >correctly positioned.
>> >
>> >> http://www.w3.org/2007/03/layerCake.png
>> >
>> >PH> Hmm, I wonder why the 'Proof' Tetris piece has
>> >> a connection to Rule without going through Unifying
>> >> Logic. That seems like a very bad decision to me
>> >
>> >Unifying Logic is the framework that includes the others
>> >as subsets: RDF, RDF-S, Rule RIF, OWL, and SPARQL.
>> >
>> >Each of these subsets is tailored for a specific kind of
>> >inference engine and/or a specific range of uses. What
>> >unifies them is the common model-theoretic semantics.
>> >That semantics enables all of them to interoperate on
>> >shared data and produce consistent results.
>>
>> Thats what I would expect, yes. And I know the overall picture. What
>> surprised me was the fact that there seems to be a special
>> short-circuit allowing Rules to connect to Proof without taking the
>> Logic into account. Which in turn suggests a special dispensation for
>> Rules to avoid having to have a common semantics with everything
>> else. As I know there are, as the popular media says, Powerful Forces
>> in the Rules meta-community which would approve of short-circuiting
>> conventional semantics altogether in favor of, say, some version of
>> Prolog, I am slightly concerned that this peculiar kink in the layer
>> cake has been put there deliberately to make it possible to do an
>> end-run around a unifying logic. Which when one takes into account
>> the whole point of "Unifying", would IMO be a pity.
>>
>> Pat
>>
>> >
>> >My suggestion would be to draw the Unifying Logic box as
>> >a large container that includes all the others inside:
>> >RDF, RDF-S, Rule RIF, OWL, and SPARQL.
>>
>> The layer-cake display has become a kind of W3C icon now.
>>
>>
>> --
>> ---------------------------------------------------------------------
>> IHMC (850)434 8903 or (650)494 3973 home
>> 40 South Alcaniz St. (850)202 4416 office
>> Pensacola (850)202 4440 fax
>> FL 32502 (850)291 0667 cell
>> phayesAT-SIGNihmc.us http://www.ihmc.us/users/phayes
>> (026)
--
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