Re: protege-discussion Digest, Vol 80, Issue 8

Hello everyone,

It took me some time to answer the replies to my previous post.  Read
below please.

On Thu, 2013-03-07 at 12:04 -0800,
[email protected] wrote:


> Today's Topics:
> 
>    1. Re: Nothing class (newbie question) (Michael DeBellis)
>    2. Re: protege-discussion Digest, Vol 80, Issue 7
>       (Andr? Luiz Tietb?hl Ramos)
>    3. Re: protege-discussion Digest, Vol 80, Issue 7 (Matthew Horridge)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> 
> As a fellow newbie one thing I find very useful is the "?" icon on any information the 
> inferencer has inferred about your ontology. You can click on that and see why it thinks some of your classes are subclasses of Nothing.?
> Michael DeBellis
> 
> --- On Wed, 3/6/13, Csongor Nyulas <[email protected]> wrote:
> 
> From: Csongor Nyulas <[email protected]>
> Subject: Re: [protege-discussion] Nothing class (newbie question)
> To: [email protected]
> Date: Wednesday, March 6, 2013, 11:55 AM
> 
> Also, if the reasoner classifies some classes as subclass of owl:Nothing 
> it means that those classes are unsatisfiable, or as Matthew said, they 
> cannot have any instances. This may be due to some modelling errors in 
> your ontology.
> 
> 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? 


> 
> On 03/06/2013 11:24 AM, Matthew Horridge wrote:
> > 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.
> >
> > Cheers,
> >
> > Matthew
> >
> >
> >
> > On 6 Mar 2013, at 11:12, Andr? Luiz Tietb?hl Ramos wrote:
> >
> >> Hello,
> >>
> >> What does the Nothing class mean actually?? Assuming its superclasses are inferred, I have many in it and do not know what this aspect means for sure.
> >>
> >> Thanks in advance.
> >>
> >> -- 
> >> Andr? Luiz Tietb?hl Ramos
> >> http://www.feng.pucrs.br/~andreltr
> 
> On Wed, 2013-03-06 at 12:04 -0800,
> [email protected] 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?
> 
> Message: 4
> Date: Wed, 06 Mar 2013 11:55:56 -0800
> From: Csongor Nyulas <[email protected]>
> To: [email protected]
> Subject: Re: [protege-discussion] Nothing class (newbie question)
> Message-ID: <[email protected]>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 
> Also, if the reasoner classifies some classes as subclass of
> owl:Nothing 
> it means that those classes are unsatisfiable, or as Matthew said, they 
> cannot have any instances. This may be due to some modelling errors in 
> your ontology.
> 
> Csongor
> 
> 
> Interesting opinion...  What kind of modeling errors could there be?
> Should I understand my modeling is somewhat flawed then?  As it is it
> seems ok to me even though I'm from more computer programming/modeling
> focus, UML specifically.
> 


-- 
Andre Luiz Tietbohl Ramos
http://www.feng.pucrs.br/~andreltr

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