[sc34wg3] New SAM PSIs

[Mary Nishikawa]

*LMG
>>>>A subtype loop looks as follows in LTM syntax:
>>>>
>>>>  super-sub(a : superclass, b : subclass)
>>>>  super-sub(b : superclass, a : subclass)
>>>>
>>>>(Assuming, of course, that 'super-sub', 'superclass', and 'subclass'
>>>>have been assigned the correct PSIs.)

Can you give an example of this? I do not think that this works. You can 
create a
loop, but does it have any bearing to reality?

Please convice me with a real example.
It should work in all cases of super-sub and if it doesn't then we need 
something else to describe this looping.

Of course if A=country and B=city, this can never work.

>>>*Murray
>>>Okay, so this is something that is syntactically possible but
>>>logically impossible. I'm not sure why it's proposed, unless
>>>there's some domain when something's superclass can also be a
>>>subclass of it. I can't think of any examples.

Me neither. Please show a real example. Even with Bernard's Math lesson, I 
am not convinced.
You can prove me wrong, please, but I haven't seen any examples posted here yet.


*LMG
>>DAML+OIL defines the equality between classes that way.

Please give me a reference.

Yes, if a subclass = superclass and a superclass = subclass then they are 
the same class.
and the distinctions of being super or sub disappears.


>Regardless of what DAML+OIL does, what does it *mean*? I'm
>confused. It's nonsense, AFAIK:
>
>      A is superclass of subclass B
>      B is superclass of subclass A

*Murray
>That doesn't make logical sense. (I must be missing something
>here, as defining equality of two classes based on them being
>both superclasses and subclasses of each other seems to ignore
>the very definitions of superclass and subclass.)


I agree. We would need to conclude that the distinction between super and 
sub disappears and collapses in one class.


Cheers,
Mary