Re: An object-oriented network DBMS from relational DBMS point of view

From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Mon, 19 Mar 2007 20:28:21 GMT
Message-ID: <FnCLh.12431$PV3.128080@ursa-nb00s0.nbnet.nb.ca>

Alfredo Novoa wrote:

> On 19 mar, 16:48, "Daniel" <danielapar..._at_gmail.com> wrote:
>

>>I hope you agree that the concept of an instance of an ADT is
>>absolutely clear.

>
> "Instance" is a synonym of "object" and it has the very same
> fuzziness.
>
> I think that "instance" is a lot worse than "object". Object could be
> acceptable as a truly synonym of "value".
>
> "To instantiate" means to give an example, and it is not an apt for
> mathematics term.

Actually, "instance" and "instantiate" come from logic, and in logic, instances are values. However, OO abuses these words as badly as it abuses so many others.

>> The only
>>issue as far as I can see is how we relate the term "instance" to the
>>terms "value" and "variable".  I think it's generally stated that an
>>"instance" is a value.  Do you disagree?

>
> Completely. I have readen "instance creation" plenty of times and
> values can't be created.
>
> Let's see the Java spec again:
>
> "A class instance is explicitly created by a class instance creation
> expression"
>
> Like:
>
> Point point = new Point(0, 0);
>
> Here we have created a variable (instance) named "point" assigning the
> "ethernal" value Point(0, 0) to it.
>
> "point" is an object. Isn't it?
>
>

>>Maybe you can clarify, is "value" typically taken as a primitive
>>concept, or can it be defined axiomatically?

>
> Primitive.

Extremely primitive. Mathematics itself depends on values at a fundamental level. Received on Mon Mar 19 2007 - 15:28:21 CDT