Re: Does Codd's view of a relational database differ from that ofDate&Darwin?[M.Gittens]

"Jan Hidders" <jan.hidders_at_REMOVETHIS.pandora.be> wrote in message news:35Iue.128265$BB4.7099455_at_phobos.telenet-ops.be...
> vc wrote:
>> My claim, so far, has been that since 'print'
>> is a pure and unmitigated imperative word, the whole construct ('for
>> each ... print') should be treated as having side effects, that is,
>> non-declarative.
>
> Well, well, well. It seems I am going to have to recant. Not that I
> completely agree with the above,

You are stubborn ;) I agree (unless I forgot something and there is another dirty word like 'print') that Daplex can be thought of as mainly declarative. However, one function (or 'keyword') like 'print' is enough to pollute the whole expression. (or the entire language), and 'print' plays rather a prominent role in constructing queries. Now, the defunct OQL is another matter. I'd be hard pressed to find an imperative bit there.

> That ruins a substantial amount of optimization possibilities and, hence,
> cannot in any way be called declarative.
>

Thank you.

>> The same holds true for the 'return' in XQuery (sorry I missed your
>> earlier message asking why I do not think XQuery is pure declarative).
>
> I still think that *that* is nonsense.

Maybe. Now that we are done with Daplex, let's talk about XQuery ;)

I say 'return' works in a way similar to print, namely creating a side effect, changing the 'world' as it were, thereby destroying XQuery expression declarativity. What's your interpretation of return ? ( I want to say right away, to save us some time, that I believe one cannot interpret 'return' as the monadic return function.).

> There are operations in XQuery that have side effects, but the return
> clause is not one of them. The strange thing about the side effects in
> XQuery, by the way, is that they actually don't seem to make the language
> much less declarative or less functional.

I do not know XQuery very well. What other [than return] side-effect operations do you have in mind ?

vc

>
> -- Jan Hidders
Received on Fri Jun 24 2005 - 03:49:23 CEST