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[protege-owl] Closed world/Open world

Timothy Redmond tredmond at stanford.edu
Mon Oct 6 10:13:21 PDT 2008


> I have seen this statement for several years now, but I am curious-- 
> what is it about OWL in particular that would prevent a reasoner  
> from treating the given ontology and data in a closed-world  
> fashion?  I don't understand how OWL itself enforces open world  
> reasoning; it seems that a reasoner could implement a mode that  
> treats the data as complete (closed).  Why is this not possible?

Two things.  First the job of a reasoner is determined by the meaning  
of the language over which it is reasoning.  So for owl, much of the  
work has been in defining the semantics ([1] for owl 1.0 and [2] for  
owl 2.0).  This existing work gives a semantics that has an open world  
behavior.  If you want to create a reasoner that does closed world  
reasoning then you would have to introduce another semantics for the  
language.  There are some ideas on how to introduce closed world  
capabilities to the owl language but as far as I know we are not close  
to adding these to capabilities to the language.

Second, I suspect that doing a good job of a closed world semantics is  
more difficult than the open world assumption.  The semantics of owl  
for example is pretty simple.  (Though there is a great deal of  
attention to  detail that is needed to meet all the different  
requirements on the language.)  But a the semantics of a logic like  
frame logic [3] which attempts to capture closed world assumptions  
and  non-monotonic reasoning is  much more complicated.

-Timothy


[1] http://www.w3.org/TR/owl-semantics/
[2] http://www.w3.org/TR/owl2-semantics/
[3] http://www.cs.umbc.edu/771/papers/flogic.pdf

On Oct 5, 2008, at 6:11 PM, James A Miller wrote:

>
> Hello everyone,
>
> This is a follow-up to a statement (from Thomas Russ)  in an earlier  
> post:
>
> "Well, that seems to rely on closed-world reasoning, which is also not
> supported in OWL."
>
> I have seen this statement for several years now, but I am curious-- 
> what is it about OWL in particular that would prevent a reasoner  
> from treating the given ontology and data in a closed-world  
> fashion?  I don't understand how OWL itself enforces open world  
> reasoning; it seems that a reasoner could implement a mode that  
> treats the data as complete (closed).  Why is this not possible?
>
> Jim
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