Re: General semantics

On 27 mei, 01:15, r..._at_raampje.lan (Reinier Post) wrote:
> Erwin wrote:
>
> You are thinking in terms of a possible implementation.
> It's more general and hence more useful to discuss this
> from an algebraic point of view instead.

> You are interpreting in terms of a possible implementation, but I am not.
> I don't know if any tables are being kept anywhere.
> I am merely saying that refererences, like OIDs, are a value domain
> on which equality comparison is meaningful, but numerical interpretation
> (e.g. greater than, addition and subtraction) is not.

> Hmmm ... yes, referencing and dereferencing is possible.
> I meant to say that treating them as numbers or even as ordered is not.

Fair enough.

A reference value is a value from a domain called 'reference', and there exists an operator DEREF that can be applied to reference values.

What is the type of value returned by DEREF ?

And all the others questions and issues raised in the TTM section that discusses variables of type POINTER_TO_CIRCLE and POINTER_TO_ELLIPSE. (The word 'pointer' in those names really means 'references', not 'pointers' in the C sense). I cannot tell from here whether you've read that, but if you haven't you might be interested, and if you have, you might be interested to look at it again.

> But this certainly isn't true.  It's important that we can tell the
> difference between aliasing and copying of object values.

It's important (perhaps) inside an OO engine running programs, and thus it is important for the OO languages concerned to have the needed syntactical constructs to give the programmer the possibility to control what will be happening inside said OO engine. At any rate, none of this warrants the originally made claim that OIDs can be useful in a database context.

Databases are collections of assertions of fact, not collections of references to assertions of fact. Received on Thu May 27 2010 - 11:16:25 CEST