Re: Extending my question. Was: The relational model and relational algebra - why did SQL become the industry standard?

"Jan Hidders" <jan.hidders_at_REMOVE.THIS.ua.ac.be> wrote in message news:3e6c873e.0_at_news.ruca.ua.ac.be...
> Lauri Pietarinen wrote:
> >Jan Hidders wrote:
> >>
> >>>>What makes you think that while-loops raise the level of abstraction?
> >>>>
> >>>What makes you think they don't?
> >>
> >>They are both imperative programming constructs.
> >>
> >That would impy that a Turing-machine program and a Java-program are on
the
> >same level of abstraction. They are both imperative programming
constructs,
> >are they not?
>
> No. A transition table from a Turing machine is not what I would call an
> imperative programming language. But anyway, you made the claim, you have
to
> provide the arguments.

If you don't mind, I will offer Lauri a little help on this one. From dictionary.com:

<definition>
2. (Metaph.) The act process of leaving out of consideration one or more properties of a complex object so as to attend to others; analysis. Thus, when the mind considers the form of a tree by itself, or the color of the leaves as separate from their size or figure, the act is called abstraction. So, also, when it considers whiteness, softness, virtue, existence, as separate from any particular objects.

Note: Abstraction is necessary to classification, by which things are arranged in genera and species. We separate in idea the qualities of certain objects, which are of the same kind, from others which are different, in each, and arrange the objects having the same properties in a class, or collected body.

Abstraction is no positive act: it is simply the negative of attention. --Sir W. Hamilton.
</definition>

A while loop leaves out of consideration several underlying comparison and branching operations as well as branching destinations so as to attend to the overall operation of repeating a given sequence of steps.

A goto statement is a direct encoding of an unconditional branch as one might use in conjunction with comparison operations and conditional branches to implement a similar repetition.

It seems rather self-evident to me. Are you satisfied with Lauri's earlier statement now? Received on Mon Mar 10 2003 - 16:54:12 CET