[cap-talk] "Composite", was "Same" key

[David Hopwood]

Mark S. Miller wrote:
> Charles Landau wrote:
> 
>> No, I think the choices are:
>>
>>                1                          >1                 >=1
>> 1 (MarkM)   Object                   Composite           ?
>> 2 (Hopwood) Object or Abstraction    Abstraction         Abstraction
>> 3 (Landau)  Atomic object            Composite object    Object
> 
> I'd represent my position as
> 
>                  1                        >=0
>     (MarkM)   Object                   Composite
> 
> This is consistent with my
> 
> # For compactness of description, we often aggregate a set of objects into
> # a composite.
> 
> which is not meant to exclude the null set.

What composite does the set of zero objects implement? If there were some
technical advantage in including the null set, that would be fine, but I
don't see any.

> This is important when using
> aggregation to reason about a multiplicity of concrete situations. Fred
> makes much use of such abstraction-by-aggregation in his thesis.

<http://www.info.ucl.ac.be/~fsp/fsp_thesis.pdf>

> Imagine how much more complex Fred's reasoning would need to be if his
> aggregates could only describe non-empty sets of objects.

I agree that a SCOLL aggregate entity should allow the empty set of objects
(which holds no permissions), but it would be perfectly reasonable to allow
that while saying that such a set does not implement a composite.

> I do not dispute that this makes the "composite" term yet stranger from
> a conventional English usage perspective. But I don't think any of the
> alternatives proposed so far are better.

What do you see as being the disadvantages of "abstraction"?

(So far, the only disadvantage that has been put forward for "abstraction" is
that it may be too general. That seems less serious to me than conflicts with
either common English usage, or OO programming language terminology.)

-- 
David Hopwood <david.nospam.hopwood at blueyonder.co.uk>