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

On Mar 19, 2:01 pm, "Alfredo Novoa" <alfred..._at_gmail.com> 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'm not referring to intuitive notions, the algebraic specification of ADT's is well understood, there's a literature on that subject. If you don't have some basic familiarity with that literature and its terminology, it's difficult to have a meaningful discussion.

> values can't be created.

I think this statement belongs to the world of intuitive notions rather than algebraic specifications, but let me just ask you two questions (and they are questions, I'm not trying to make a point):

Are you saying that it is not meaningful to talk about manufacturing a custom value as an aggregate of atomic values such as 1.0, "Jun 1, 2007", and 33?

Do you think it is meaningful to talk about storing a value in a location in computer memory?
>
> 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?

In Java, it would be more accurate to say that point is a variable that holds a reference to (the address of) a Point object.
>
> > Maybe you can clarify, is "value" typically taken as a primitive
> > concept, or can it be defined axiomatically?
>
> Primitive.
>
Even so, it might be helpful to enumerate the properties that a thing must have to be regarded as value, immutability, etc. Then we can ask whether an instance of an ADT satisfies those properties.

Best regards,
Daniel Parker Received on Mon Mar 19 2007 - 21:21:31 CET