[sc34wg3] New SAM PSIs

[Dmitry]

[Murray Altheim]
> |
> | I think you're now missing my point: the "superclass-subclass loop"
> | is simply wrong.

[ Lars Marius Garshol]
> We've known each other for long enough now that you should have
> learned that arguments are the only things that work with me. I don't
> listen to assertions unsupported by argument. (Whether you care about
> that is another matter, of course.)
>
[Murray Altheim]
> | The whole idea only makes sense in terms of "superset-subset loop."
>
[ Lars Marius Garshol]
> In one sense that's what it is. Superclass/subclass is, in the strict
> logical sense, only a statement about the extensions of the classes,
> which are of course sets.

I think that there are two different models which are discussed in this
thread.

More precisely, I think that:

It is possible to create different models explaining "class-subclass","
instance-class" relationships.

It is possible to create useful model (let's call it M0) of "class-subclass"
," instance-class" relationships that is not based on concept of extensions.
This model does not have superclass-subclass loops by definition.

Class-subclass model used in SAM (M1) is out of scope of M0, it is a
different model with different "axioms". I guess one of the first "axioms"
of M1 is that "A type is a set of individual subjects, each of which is an
instance of the type."

M0 and M1 use the same terms "class", "subclass", "type", "subtype" but
because of different "axioms" these terms have different meaning.  It is
"difficult" to discuss M1 and M0 as one model.

Question that I have: Do we want to discuss M0 if we know that SAM is based
on M1?


Dmitry