[sc34wg3] irreflexive isa

[Lars Marius Garshol]

* Robert Barta
>
> And I see now that TMDM does that too:
>
>   http://www.isotopicmaps.org/sam/sam-model/#sect-types
>
>   A topic type is a subject that captures some commonality in a set
>   of subjects.
>
> According to "normal" set theory, the set is never part of itself. In
> other words, the isa relation between the set and elements of that set
> is always is irreflexive.

Actually, this is not a violation of set theory. Here is what we have:

   A topic type: a subject that captures some commonality in a set
                 of subjects

   A set of subjects: basically, the instances of the topic type

Now, you'll note that the topic type itself is not described as a set,  
but rather as "a <something> that captures a commonality".

So if the topic type were an instance of itself, the set would contain  
the topic type, yes, but it wouldn't be a set containing itself.

So I don't see any problem here.

--Lars M.
http://www.garshol.priv.no/tmphoto/
http://www.garshol.priv.no/blog/