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Re: Elegant solution to let OWL/RDF cover Closed World Assumptions (CWA), incl unique Name Assumption (UNA)

From: Pascal Hitzler <pascal.hitzler@wright.edu>
Date: Fri, 19 Nov 2010 11:33:59 -0500
To: DJA222 <dja222@hotmail.com>
Cc: public-owl-comments@w3.org
Message-id: <4CE6A6F7.6020007@wright.edu>


On 11/19/2010 11:15 AM, DJA222 wrote:
> Dear Pascal and Jie,
>
> Thank you very much for your response. To my great relief I found out
> that it is a hot topic and that it indeed has W3C's full attention.
>
> As to Pascals last remark "...it needs spelling out explicitly...",
> I'd like to give a small example.

What I mean with "spelling out explicitly" is - concrete proposals are 
needed (syntax + formal semantics) together with evidence of 
implementability in a reasonable way. Or at least that's the first step :)

> Assume a class Person with 10
> pre-defined individuals, 4 have the property+value "isMale true", 4
> have "isMale false" and 2 don't have the property "isMale" at all. If
> one takes the Open World Assumption (OWA) VERY literally (i.e. into
> the extreme), then during instantiation of a class expression "Person
> and (isMale value true)", the reasoner (Fact++, Pellet, etc.) might
> reason as follows: I indeed see 4 individuals that have the
> property+value "isMale true" visible(/explicitly) and the rest that
> have either another visible value for this property or don't have the
> property visible at all. But applying OWA (into the extreme) ,now who
> doesn't tell me that the other individuals don't have some hidden
> "isMale true" that I cannot see? Ergo: I can't give a result at all!

That fortunately won't happen :) You do get the 4 results for which it 
is known, and that's fine.

> But it DOES give a result, namely the 4 individuals with "isMale
> true"! I.m.h.o: isn't this a result that stems from Closed World
> Assumption (CWA) or do I overlook something essential ?!

I wouldn't think so. It would be closed world if the reply would also 
state: "These are all that have this property". The response, however, 
comes with an implicit: "These are all of which I know that they have 
this property" which is completely in synch with the OWA.

Pascal.

> Many thanks in advance, Best Regards, DJ
>
>
>
>
> From: Jie Bao Sent: Friday, November 19, 2010 3:16 PM To: Pascal
> Hitzler Cc: DJA222 ; public-owl-comments@w3.org Subject: Re: Elegant
> solution to let OWL/RDF cover Closed World Assumptions (CWA), incl
> unique Name Assumption (UNA)
>
>
> In similar spirit, axioms with CWA and UNA can be seen as special
> cases of integrity constraints. A semantics is proposed in [1]. DJ's
> proposal gave it a syntax.
>
>
> [1] http://www.cs.rpi.edu/~taoj2/publications/IC-AAAI-2010.pdf
>
>
> Regards Jie
>
>
>
> On Thu, Nov 18, 2010 at 14:01, Pascal
> Hitzler<pascal.hitzler@wright.edu>  wrote:
>
> It has indeed crossed my mind (and that of some of the people I've
> been talking with) that one may want to have a simple "closure" -
> i.e., something much simpler than what most non-monotonic formalisms
> provide. It seems, though, that some of the things you describe below
> can be achieved by the autoepistemic K operator [1,2], by DL-safe
> variables [3,4], or the approach proposed in [5]. In any case, it
> needs spelling out explicitly...
>
> Best Regards,
>
> Pascal.
>
>
> [1] http://portal.acm.org/citation.cfm?doid=1754399.1754403
>
> [2]
> http://knoesis.wright.edu/faculty/pascal/resources/publications/mknftheo.pdf
>
>  [3]
> http://knoesis.wright.edu/faculty/pascal/resources/publications/ELP_iswc08.pdf
>
>  [4] http://korrekt.org/page/Description_Logic_Rules_%28monograph%29
>
> [5]
> http://knoesis.wright.edu/faculty/pascal/resources/publications/ELP2.pdf
>
>
>
>
>
> On 11/16/2010 12:52 PM, DJA222 wrote:
>
> Dear OWL Staff,
>
> Hereby I would like to suggest an elegant solution to let OWL/RDF
> cover Closed World Assumptions (CWA), incl Unique Name Assumption
> (UNA).
>
> Due to its Open World Assumption (OWA), OWL/RDF  can hardly be used
> for e.g.: 1. finding (:instantiating) pre-defined individuals with a
> certain number of properties or without these properties at all
> (e.g. cardinality 0). 2. validation. OWL/RDF's OWA asserts that
> everything is possible (->infinite) until asserted otherwise by
> constraints (->finite). But doesn't infinity envelopes finity? Isn't
> processing things in a finite world (CWA) just a valid part of the
> infinite world (OWA)? Finite means that things are or (immidiately)
> can be made explicit. Then why not simply introduce a term like
> e.g."Explicit" that can be added to every constraint and applies to
> things/values that are visible at the very moment of instantiation?
>
> Example class expression: Person and (hasChild exactly 0 Explicit) :
> at the very moment that this class is being instantiated it "scans"
> for (pre-definied) individuals in class Person for which the
> property "hasChild" is explicitly absent (:exactly 0 Explicit).
> Although OWL/RDF itself leaves open the possibility that the
> individuals still might have hidden "hasChild" properties, the
> reasoner just looks for explicitly absent properties because the
> class expression tells it to do so.
>
> This way it can also be used for validation/integrity-check  with a
> class expression with "Explicit" included: if something is asserted,
> that can't be derived from explicitly present assertions at the very
> moment of instantiation, than this will be reported: NOT as being a
> OWL/RDF error/conflict/inconsistency, but just as a note to the user
> who fabricated this class expression. Again, without OWL/RDF itself
> denying that there might still be assertions that are just not
> visible at the moment of instantiation.
>
> Same story for UNA: by adding a term like e.g. "Unique" in a class
> expression it might notify the user (who wrote the expression) upon
> instantiation, that it has found individuals who are asserted
> (directly or implied) to be identical but have different names or
> that it has found more individuals than expected. Again, without
> OWL/RDF itself denying that there might by assertions that are just
> not visible at the moment of instantiation.
>
> All above OWL/RDF examples would still comply with OWA and Non-UNA
> demands, by assuming the possible outcome (with the terms "Explicit"
> and "Unique" used in expressions) not as OWL/RDF conlicts, but just
> as (user) notifications.
>
> Above is extremely important in research where INDIVIDUALS and
> relations between them are at the focus, instead of the more generic
> class approach. In certain researches,  thousands and thousands of
> data snippets (:Individuals) come in from different places and you
> want to look for certain properties/relations that these pieces
> share/have with/to one another. This can not easily be automated
> with present OWL/RDF. Yes, one might use SPARQL in some ways, but the
> aim is to let simple class instantiation do its work.
>
> In my conviction, with a slight addition, OWL/RDF semantics can
> proof to be a more complete basis for ANY semantic real world
> application and solution, and not just for a limited part!
>
> Hopefully you might reconsider this idea, or find find some similar
> solution, that really is in the need of many (potential) OWL/RDF
> practitioners.
>
> Sincerely yours,
>
> DJ Alexander
>
>
>
> -- Prof. Dr. Pascal Hitzler Dept. of Computer Science, Wright State
> University, Dayton, OH pascal@pascal-hitzler.de
> http://www.knoesis.org/pascal/ Semantic Web Textbook:
> http://www.semantic-web-book.org Semantic Web Journal:
> http://www.semantic-web-journal.net
>
>
>
>

-- 
Prof. Dr. Pascal Hitzler
Dept. of Computer Science, Wright State University, Dayton, OH
pascal@pascal-hitzler.de   http://www.knoesis.org/pascal/
Semantic Web Textbook: http://www.semantic-web-book.org
Semantic Web Journal: http://www.semantic-web-journal.net
Received on Friday, 19 November 2010 16:34:33 GMT

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