Re: Self pointer in limited record

[Jean-Pierre Rosen <rosen@adalog.fr>]

Dmitry A. Kazakov a �crit :
> 1. a concept or idea not associated with any specific instance; "he loved
> her only in the abstract--not in person"
> 
> 2. the act of withdrawing or removing something
> 
> 3. the process of formulating general concepts by abstracting common
> properties of instances
> 
> 4. an abstract painting
> 
> 5. preoccupation with something to the exclusion of all else
> 
> 6. a general concept formed by extracting common features from specific
> examples
Interesting...

>> But an abstraction (as I -and apparently others- understand it) is a 
>> reduced view of a real world *object*.
> 
> This is close the position 2. Mine is under 1 and 6 and Georg's is under 3.
Yes. This is also the ethymological meaning: abs-tractare (latin) means 
"to withdraw from"

> None of standard meanings 1-6 can be thought on the basis of single
> instance. 
2 certainly can. The idea is that you cannot put "Spike the dog" into 
your computer; what you can do is put some characteristics of it in the 
form of data that are of interest from the point of view of your 
program. You therefore abstract away all the uninteresting properties.

> The dictionary explicitly refers to "instances" and "examples."
> Even treating abstraction exclusively as modeling with removing something
> in order to model (though why couldn't we add something?)
How could you have something in the model that is not in what you are 
modelling?

> , even when
> abstraction = moving from one substrate to another, one have to model not
> only the object, but the relations it participates with other objects.
But you can have relations between instances, not necessarily between 
classes. If I walk Spike, it is a relation between an instance of a 
human being and an instance of a dogan being :-)

-- 
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            J-P. Rosen (rosen@adalog.fr)
Visit Adalog's web site at http://www.adalog.fr