[sc34wg3] irreflexive isa

[Patrick Durusau]

Lars,

Lars Marius Garshol wrote:
> * 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.
>
>   
Well, there isn't a problem because apparently both the TMDM and TMRM 
use irreflexive isa. Note the rest of Robert's post noted:

> And further it strengthens also
> >
> >    .... A topic type may itself be an instance of another topic type, ....
> >
> > It does not say
> >
> >     .... be an instance of any other topic ...
> >
> > TMDM uses the word ... another ...
> >
> > So it is fair to assume that irreflexive is intended.
Had reflexive isa been intended the language would read: "A topic type 
may be an instance of itself or of another topic type."

In any event, this is a mapping question between the TMDM and the TMRM.

BTW, the TMRM is not an attempt to be a universal data model (from your 
original post on this issue).

It is an attempt to describe the disclosure of the subjects that make up 
any data model (and by extension the subjects that data model 
represents). Quite a different thing.

Integration requires 1) that everyone use the same data model (highly 
unlikely) or 2) disclosure of the subjects that make up data models (and 
the subjects they represent) so that reliable mappings can be created 
between them.

The TMDM defining a way to create mappings between identified subjects, 
for instance. But that requires a definition of a means of 
identification and definitions of equivalence, for which the TMRM 
defines disclosure but doesn't define itself.

The latter seems more feasible to me but that should come as no surprise.

Hope you are having a great day!

Patrick

PS: Breaking for meetings. Won't be back online, reliably, until this 
evening my local time. (East Coast, US)
> --Lars M.
> http://www.garshol.priv.no/tmphoto/
> http://www.garshol.priv.no/blog/
>
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>   

-- 
Patrick Durusau
patrick at durusau.net
Chair, V1 - US TAG to JTC 1/SC 34
Convener, JTC 1/SC 34/WG 3 (Topic Maps)
Editor, OpenDocument Format TC (OASIS), Project Editor ISO/IEC 26300
Co-Editor, ISO/IEC 13250-1, 13250-5 (Topic Maps)