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[protege-discussion] Doubt about information structure

André Luiz Tietböhl Ramos andreltramos at gmail.com
Wed Apr 10 05:57:21 PDT 2013


On Tue, 2013-04-09 at 05:04 -0700,
protege-discussion-request at lists.stanford.edu wrote:


> Today's Topics:
> 
>    1. Re: protege-discussion Digest, Vol 80, Issue 8 (Csongor Nyulas)
> >>
> >> Csongor
> >
> > Thanks Csongor.  As far as my limited knowledge goes in this subject, 
> > I don't understand the satisfiable/unsatisfiable concept.  
> > "Structure-wise" the classes' tree seems ok to me.  You
> > meant that instances are be developed in the sense of having 
> > individuals linked to them or by linking to other classes which are 
> > then part of given individuals' links?  In fact, the
> > instance concept is not very clear to me, sorry.  I don't see any a 
> > "more defined" concept than data and object properties (which aren't 
> > used for instances I suppose)
> > and individuals.  BTW, do you consider individuals as instances?
> 
> I think the best would be if you would read an OWL Tutorial. [1] is 
> quite comprehensive, [2] is less detailed but more visual and explains 
> SWRL too, and [3] is useful if you want to understand the OWL language.
> 
> And yes, when I used instance I meant individual. In OWL the instances 
> of a class are called individuals.


Ok, thanks Csongor.  In addition, thank you for suggesting the OWL
Tutorial which has been very useful.


> >> On Wed, 2013-03-06 at 12:04 -0800,
> >> protege-discussion-request at lists.stanford.edu  <mailto:protege-discussion-request at lists.stanford.edu>  wrote:
> >> > Message: 2
> >> >
> >> > Hi,
> >> >
> >> > owl:Nothing is interpreted as the empty set.  It does not have any instances.  Because it is
> >> > interpreted as the empty set, it is a subclass of every other class (since the empty set is a
> >> > subset of every set).  owl:Thing appears at the top of the class hierarchy, whilst owl:Nothing
> >> > appears at the bottom of the class hierarchy.  Hope this helps.
> >>
> >>
> >> Yes, it does.  I don't think this matters much though but the Nothing is
> >> shown in the top of the tree and in red.  Since I'm just beginning  I'm
> >> modeling as much as I can using classes and leaving individuals for a
> >> step later.  In other words, how to define an instance although at this
> >> point I don't need them AFAIK?
> 
> Even if you don't define any individuals in an ontology yourself, a 
> reasoner can detect that some classes are defined in a way that it is 
> impossible for those classes to have any instances (i.e. no individual 
> can possible belong to that class).


Suppose I do not define some individuals related to a given class, or
classes, in an ontology consequently I'm assuming they'll be inferred as
subclasses of the Nothing, correct?  Is it a mandatory condition to
avoid classes being inferred as subclasses of the Nothing class that
there are relationships between them and a individuals?  Theoretically,
is it possible to have a class that is purely conceptual thus is it is
not linked to any individual?  Would this condition mean it is an error
in boolean sense?

Thanks,

-- 
André Luiz Tietböhl Ramos
http://www.feng.pucrs.br/~andreltr 

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