W3C home > Mailing lists > Public > public-owl-comments@w3.org > November 2010

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: Thu, 18 Nov 2010 14:01:57 -0500
To: DJA222 <dja222@hotmail.com>
Cc: public-owl-comments@w3.org
Message-id: <4CE57825.2030109@wright.edu>
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
Received on Thursday, 18 November 2010 19:02:29 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Thursday, 18 November 2010 19:02:30 GMT