Re: [Chebi-ontology] Oxygen-18 to isotope: instance or subclass?

[Barry S. <phi...@bu...>]

Given what Alan says, I infer that it must be incorrect to assert that
oxygen-18 is an instance of anything. Certainly there are instances of
oxygen-18, but oxygen-18 itself is for that very reason not itself an
instance
BS


On Fri, Aug 29, 2014 at 4:36 PM, Alan Ruttenberg <ala...@gm...>
wrote:

>
>
>
> On Fri, Aug 29, 2014 at 10:44 AM, Barry Smith <phi...@bu...>
> wrote:
>
>> Re: the issue raised by:
>>
>> ​    oxygen-18
>> *        subclass of* oxygen
>>         *instance of* isotope​
>>
>> ​can I ask that people help me get clear about the background:
>>
>> (a) is it the case that all of these expressions refer to general
>> entities which have many many particular instances
>>
>
> yes
>
>  (b) is it the case ​that every instance of oxygen-18 is also an instance
>> of isotope
>>
>
> to be an isotope is something like to be a mutation. To be a mutation is
> to be slightly different from the canonical, but of equal status except for
> perhaps the number of class members. To be an instance of an isotope of
> oxygen (atom) is to be a an atom with a different number of nucleons
> (protons and neutrons)  than the most abundant form (oxygen-16, with 8
> protons and 8 neutrons in its nucleus).
>
> One might argue that the number of nucleons is a quality of anything
> oxygen, of which I list a variety of entities that ChEBI represents in an
> earlier message.
>
>
>> ​(c) if yes, then why not just assert 'subclass of' throughout?
>>
>
> You can, just as you can say that red balls are a subclass of colored
> things ;-)
>
> -Alan
>
>
>>
>>
>> BS​
>>
>>
>>
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>