Unique Name Assumption

[Alexandre RICHARD]

First of all, thanks for the remark on the unique name assumption, I 
had forgotten that issue. As for disjointing systematically... well, I 
agree for the instances but for classes, it depends if you actually can 
afford them to be disjoints.


About the point Ed was making, I certainly agree with his example as it 
is valid and the use of instances for atomic elements is indeed a bad 
idea if, for instance, different isotopic species are to be taken into 
account, but then again this is not the case for us, at least currently.
(as for the specific carbon atom example, I am sorry but I fail to 
understand why would someone would have (or at least feel an urge) to 
link a specific atom to an ontology dedicated to astronomical object 
types. But, being no astronomer, I may just be missing something here.)

Last but not least, I will have to disagree to this:
"We should refrain from using individuals except for a named individual 
in the  universe: Earth, Algol, M31, Mike Brown, MyBigRedChair."
Individuals are certainly to be used with caution but I do not see any 
problem with using individuals instead of a class which would actually 
have only one individual. To re-use the carbon element example:
- if your field of application includes isotopes then you obviously 
cannot use an individual for the carbon element
- if your field only requires the carbon element without anymore 
details, then you can use an individual since if you create a class for 
the carbon element it will have only one individual in its extension 
(in fact in a case like this, from a strict DL representation you 
actually should use an individual... but as usual the choice is often 
motivated by performances factors such as the overall complexity of the 
DL used and the kind of inferences to make)

All of this to say that I understand your concerns, Ed, but if I am not 
mistaken you are working on ontologies for the Astronomy field with an 
objective of creating a rather complete and universal structure whereas 
I am working on a very small, dedicated structure to be used as a 
limited but fast and powerful tool for inference on astronomical object 
types only. Certainly both of our works have numerous similarities, but 
your limitations and issues are vastly different from mine, which is 
why I sometimes have to disagree.


Cheers,

Alexander
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Quoting Elyes Lehtihet <lehtihet at iie.cnam.fr>:

> Even by using Classes you will still have to deal with the unique name
> assumption. Again the only solution is to add systematically
> 'owl:AllDisjoint' axioms between sibling classes - that should work if
> you are not using too much multiple inheritance... the reasoner will
> eventually infer inconsistencies...
>
> All the best,
> Elyes
>
> ------------- On 18/04/2007 22:40,Ed Shaya wrote:
>> It does not seem to me to be a good idea to make individual 
>> elements/atoms instances in the first place.  What if someone needs 
>> to refer to a specific atom sitting in their Atomic Force Microscope 
>> (AFM)?  For this you would want to make an individual of the Class 
>> Carbon.
>> <Carbon rdf:ID="MyCarbonAtom"/> where Carbon is a class.  This also 
>> makes it possible to add isotopic species as subclasses.  We should 
>> refrain from using individuals except for a named individual in the 
>> universe: Earth, Algol, M31, Mike Brown, MyBigRedChair.
>>
>> One still should make the various types of atoms owl:disjointWith, 
>> but, as I mentioned previously, we really need a new version of OWL 
>> to make this more manageable because nearly every class is distinct 
>> from every other class in astronomy.  In any event the only loss if 
>> you do not use disjointWith is that a reasoner can not spot an error 
>> if someone tries MyCarbonAtom is both Carbon and Silicon.
>>
>> Ed
>>
>>
>> Thanks, Elyes for pointing out a weakness here.
>> Ed
>>
>>
>> Elyes Lehtihet wrote:
>>> Hello,
>>>
>>> While exploring the AstroOntology, I have noticed that you create a 
>>> set of individuals (instances) of the AtomicElement, SpectralType, 
>>> etc. As you probably know, the web ontology language use the Unique 
>>> Name Assumption: every concept is not, by default, necessary 
>>> distinct from the others. It implies that the instances of your 
>>> classes are not made 'explicitly' distinct for the reasoners : 
>>> Carbon is not explicitly distinct from Calcium, etc. etc.
>>>
>>> The common pattern to solve this problem is to create an 
>>> 'owl:AllDifferents' axiom (Protégé: OWL/Edit owl:AllDifferents...) 
>>> that regroups the set of instances. After, one should create a new 
>>> expression to enumerate the allowed values of the class. Example 
>>> for the LuminosityClass: {LuminosityClassII LuminosityClassV 
>>> LuminosityClassIII LuminosityClassIV LuminosityClassI}
>>> This method assumes that a Class cannot take other values than the 
>>> ones explicitly defined by the enumeration - But maybe there are 
>>> more AtomicElement than the 14 that are cited :-)
>>>
>>> Best regards,
>>> Elyes
>>>
>