Re: "OWL" Entailment

On 5/6/09 1:14 PM, "Bijan Parsia" <bparsia@cs.man.ac.uk> wrote:
> There are some questions that pretty much all more or less expressive
> entailment regimes have to answer to be a sane SPARQL entailment regime:
> 
> 1) If you entail BNodes, what/how many BNodes do you return?
> Example (Simple Entailment):
> s p o entails  s p _:g.
> Should SELECT ?X WHERE {s p ?X} return both s and _:g? (No!)

Agreed.
 
> Compare with:
> s p o.
> s p _:g.
> Where we do *now* get 2 answers (and should).

Agreed.
 
> Example (OWL):
> s rdf:type [a owl:Restriction;
> owl:onProperty :p;
> owl:someValuesFrom owl:Thing]
> entails s p _:g.
> 
> Should SELECT ?X WHERE {s p ?X} return anything? (I say no)

Hmm.. This is tricky.  Can you elaborate on why you think there shouldn't be
any answers here.  I understand that the same argument for the first example
(simple entailment) would apply here, but intuitively it seems to me that a
user-specified existential restriction in this case is more 'suggestive'
(for lack of a better word - I really don't have any principled reason other
than intuition regarding the OWL author's intent) of the s p _:g entailment.

For example, consider:

Brain rdfs:subClassOf [
  a owl:Restriction;
  owl:onProperty part_of;
  owl:someValuesFrom CentralNervousSystem
]

MyBrain a Brain

If the query,

SELECT ?ANATOMY { MyBrain part_of ?ANATOMY }

Returns nothing (as I understand your suggestion above would sanction), a
user might interpret this as suggesting that 'my brain' is not part of
anything even though the OWL axioms say it is necessarily part of the
central nervous system.

> 2) If your data is contradictory, what should you return?
> Typically, contractions entail everything, thus infinite answers.
> Obvious solution is to return a fault (with no answers) and suggest
> using a weaker entailment regime.

Agreed.
 
-- 
----------------------
Chimezie (chee-meh) Thomas-Ogbuji (oh-bu-gee)
Heart and Vascular Institute (Clinical Investigations)
Cleveland Clinic (ogbujic@ccf.org)
Ph.D. Student Case Western Reserve University
(chimezie.thomas-ogbuji@case.edu)


===================================

P Please consider the environment before printing this e-mail

Cleveland Clinic is ranked one of the top hospitals
in America by U.S. News & World Report (2008).  
Visit us online at http://www.clevelandclinic.org for
a complete listing of our services, staff and
locations.


Confidentiality Note:  This message is intended for use
only by the individual or entity to which it is addressed
and may contain information that is privileged,
confidential, and exempt from disclosure under applicable
law.  If the reader of this message is not the intended
recipient or the employee or agent responsible for
delivering the message to the intended recipient, you are
hereby notified that any dissemination, distribution or
copying of this communication is strictly prohibited.  If
you have received this communication in error,  please
contact the sender immediately and destroy the material in
its entirety, whether electronic or hard copy.  Thank you.

Received on Thursday, 7 May 2009 14:13:24 UTC