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[protege-owl] WG: owl:AllDifferent

ewallace at cme.nist.gov ewallace at cme.nist.gov
Thu Sep 7 10:12:56 PDT 2006


Raj Mudunuri wrote:

>I'm posting this again as I have not yet gotten any response so far...

That's strange.  I saw at least one response to this that explained
it pretty well.  I guess that I will try again.

The earlier posting from Raj Mudunuri included:
>I'm just pondering, why the individuals of owl ontologies in Protege are
>not assumed as different entities by default... I mean, to define that
>our individuals are different, we have to explicitely say this by using
>the owl:AllDifferent construct... I can't imagine a case where we have
>two individuals and that we want the reasoner to assume that these two
>are the same... Anyhow the reasoning is done at concept level, but when
>we start assigning individuals then we really mean that all the
>individuals are different, don't we? So the reasoner can pop up a
>warning/error when it finds that two individuals have a clash where
>these two individuals seem to be the same according to the reasoner.
>Opposite to the way it is done now, I guess!?

Reasoning can be done at concept and instance levels.  Even most
modern DL reasoners support both TBox and Abox reasoning.

The reason for no Unique Names Assumption in OWL is because it
is a Web Ontology Language.  On the web, different authors will
use different names (URIs) to identify the same concepts or individuals.
The idea is to have semantic web enabled applications to be able to
operate usefully over this distributed heterogeneous data.  There are 
many other issues to address to deal with this problem in the general
case, but the current way the reasoning works does enable machine
inference to merge data about individuals.

Since there are many cases when a particular set of individuals
described by RDF/OWL data are meant to be distinct, AllDifferent was
added to OWL to make it easier to state this.

-Evan

Evan K. Wallace
Manufacturing Systems Integration Division
NIST



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