Minsu, Sean --

Apologies Minsu, I misread your original note.  Seems like we are all on the same, nonmonotonic side.

Sean -- There's been quite a bit of discussion on the lists that should help to answer your question, below. 

My take on that discussion would be -- a conclusion that an agent draws is always to be found by closed world (NAF) reasoning, relative to the facts and rules that it has gathered in "open" mode from across the web.  In other words, it always concludes something like "as far as I know from looking at these 15 URIs at 10 am Eastern time on 20031114, there is no such thing as a unicorn, but horses do exist".

It seems to me that much of the debate around closed/open world on the semantic web would be resolved if people would agree to hang English meanings on things like p(unicorn,horse). 

Our system, Internet Business Logic, does just that, including drill down to the supporting facts.  You can try it out at www.reengineeringllc.com .  Comments gratefully received.

                                Cheers,  -- Adrian

At 03:18 PM 11/14/03 +0000, you wrote:
Err, unless it is far too late and I am missing the snake right in front of my nose, Adrian is arguing for a nonmonotonic reasoning, which is what Minsu wants.

Nonmonotonic reasoning is the ability to mkae assertions about the domain (push new facts on the stack) which may later be modified or retracted (pop the facts).

The  question I have is how often do we need open world? In other words, how often would a closed world assumption supporting logic be good enough?

Regards,
Sean

On Thursday, November 13, 2003, at 02:56 PM, Adrian Walker wrote:

Minsu --

You wrote...

Web ontologies *should* independently evolve.
In this regard, I think rule languages and processors for the semantic
web
should address problems of reasoning in the open knowledge space,
which is non-monotonic in its nature.



I often see statements of this kind from the RDF and semantic web folks.

In the real world, if I tell you that  

           can_fly(X) if bird(X) & not penguin(X)
           
           bird(Fred).

you will presumably conclude that Fred can fly.  If I later add penguin(Fred), you will no longer conclude that Fred can fly.

This may sound naive, but can you argue for me please why the above should be ruled out on the Semantic Web ?  Seems like you are throwing out the bird with the bathwater (:-)

Thanks in advance,   -- Adrian

--

              INTERNET BUSINESS LOGIC
Business Rules in English + Your Oracle Databases
            
www.reengineeringllc.com

Dr. Adrian Walker
Reengineering LLC
PO Box 1412
Bristol, CT 06011-1412, USA

Phone: 860 583 9677
Fax:   860 314 1029
Cell:  860 830 2085



[Dan Brickley wrote,]
 


* Minsu Jang <minsu@etri.re.kr> [2003-11-08 14:26+0900]
   


- OWLer: an OWL inference system. It uses JTP for inferencing.
- ezOWL: a Protege plugin for visual editing of OWL documents.
- MOA: a merging tool for merging multiple OWL ongologies.
- Buchingae: a web-friendly rule language. not XML-based.
- LogicML: a rule markup language, which is a slight extension of
RuleML's hornlog.
     


...same question as above! Where/when can we find out more?

   



Most of these are not documented well yet, but ezOWL is
published under plugins directory of Protege.
You can find more about the plugin at
http://iweb.etri.re.kr/ezowl/.

 


I notice in
   


http://machine-knows.etri.re.kr/bossam/download/download.html that
 


the engine isn't public yet. Do you have a sense for when it will be
available, or expectations about likely license terms? (opensource
   


would
 


be great...)
   



The engine will be available with the similar licensing terms to that of
Jess.

 


A technical question (for everyone, really):
The Web Ontology WG spent a lot of time and energy
on the delicate balance between OWL DL and OWL Full. Do you have any
findings from your implementation work that would help us estimate the
   



 


impact of this aspect of OWL on any future Rules standardisation? Is
it feasible to keep both traditions/approaches/communities happy
   


within
 


a single "OWL-compatible" rules language?

   



I don't have good technical background on computational logics or
mechanical theorem proving, so what I'm going to say could be
a disaster for this list. ;-) Even if so, please don't hrurry for
escaping,
but be generous enough to provide your invaluable teachings.

Bossam is just a production rule system with some extended knowledge
representation elements which make the engine suitable for inferencing
over OWL ontology. When I started to write OWL inferencing rules, I did
not
fully understand what makes OWL Full and OWL DL different.

The only thing I knew was that OWL properties, classes and individuals
are
pairwise disjoint in OWL DL, but interchangeable in OWL Full.
This discrimination rule should be reflected in OWL inferencing rules
for OWL DL.
For OWL Full, all the facts and rules of RDFS should be added, and OWL
class
should be declared to be owl:equivalentClass to rdfs:Class.

What I have found until now is that the expressiveness of rule language
is
not very different whether it's for reasoning over OWL Lite, DL or Full.
The difference lies in the rulebases. When you write a rulebase
for reasoning over OWL Lite ontology, you will end up with a smaller set
of rules.

What I have in mind from my implementation experiences is that
a single rules language is enough for OWL inference.

One thing I'd like to address at this point is that when you start to
write
rules for real applications, the situation becomes very complex.
It's not OWL inferencing, but real knowledge processing. The web is open
and many web users will want to process knowledge in the open web, which
will contain many knowledge elements which contradict each other.
Even if you preset all the ontologies for a reasoning session, the
situation
does not become more optimistic, because web ontologies are not
controlled.
Web ontologies *should* independently evolve.
In this regard, I think rule languages and processors for the semantic
web
should address problems of reasoning in the open knowledge space,
which is non-monotonic in its nature.

 


BTW http://machine-knows.etri.re.kr/bossam/docs/owlinference.html
   


doesn't
 


explicitly mention OWL DL vs Full or Lite. Which flavour(s) are you
targetting?
   



Um, I did not target any one species (:-\), but the rulebase I'm working
on is
targetting OWL Full. And I have a plan to write two more sets of rules
for
OWL DL and Lite.

Regards,
Minsu



 



--

              INTERNET BUSINESS LOGIC
Business Rules in English + Your Oracle Databases
            
www.reengineeringllc.com

Dr. Adrian Walker
Reengineering LLC
PO Box 1412
Bristol, CT 06011-1412, USA

Phone: 860 583 9677
Fax:   860 314 1029
Cell:  860 830 2085

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