Re: 1GB Tables as Classes, or Tables as Types, and all that refuted

On Sun, 12 Dec 2004 16:46:57 -0800, Costin Cozianu <c_cozianu_at_hotmail.com> wrote:

>> Object:
>>
>> Objects encapsulate both state and behavior. In particular they
>> consist of a collection of instance variables, representing the state
>> of the object, and a collection of methods, representing the behavior
>> that the object is capable of performing. The methods are routines
>> that are capable of accessing and manipulating the values of the
>> instance variables of the object...
>> As is the case in Java and Smalltalk, we wil assume that all objects
>> are implicit references...
>>
>> Class:
>>
>> Classes are extensible templates for creating objects, providing
>> initial values for instance variables and the bodies for methods. All
>> objects generated from the same class share the same methods, but
>> contain separate copies of the instance variables. New objects can be
>> created from a class by applying the new operator to the name of the
>> class.
>>
>> I have not found any definition for instance variable, and the
>> sloppiness and contradictions are evident.

>This is a bunch of BS, Alfredo.

I agree on that the definitions are not good :)

> A defintion for instance variable if Kim
>Bruce has not put it in, is trivial.

But it is essential to know what an object is for him. It is a fundamental omission.

> It's a name "x" such that given a
>reference to an object instance r, r.x can be used to denote the value

What is an object instance and what is the difference between an object instance and an object?

In the OO world, instance is often another synonym of value, state and object.

>of the component x and can also be used on the left side of the
>assignment to modify the value of the component x.

So an instance variable is a variable that is a component of a variable, so an object is a composed variable. But variables don't have methods, methods are members of types.

A few lines below he says that objects are references, he is confusing the pointer typed variables (his references) with the referenced variables (the variables formed by the collection of instance variables).

The definitions are very tied to the physical level because a logical variable does not have components, it is simply a holder for a value of some type. A value may have different representations and the representations may have components.

The class definition is terribly sloppy. He is confusing a model level concept with the source code, the language syntax and the implementation.

If he is one of the most serious OO authors what can we expect from the others?

I was looking in Pierce's papers and books but I don't find any definition of the typical OO concepts.

Regards Received on Tue Dec 14 2004 - 18:44:22 CET