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

vc wrote:
>
> I apologize for imprecise language.

No problem. As you know I'm not always too careful myself.

> So, now we have the translation:
>
> "for each x in e1 print e2" ==> [ e2 | x <- e1 ]"
>
> Let's assume that e2 = getName x. The target list will then evaluate
> to:
>
> ["John", "Peter",...,"Luke"]. Still no characters on the screen. How
> come ?

Where in the description of the semantics of DAPLEX did it say that the result must be actually printed on a screen?

But even if that were so, (it's not how people interpret it now, but it is quite possible that is how most thought about it when the language was defined) do you really think that whether things are printed on screen or just in general produced as output is an essential part of the query language? Would the language change radically if we changed that? Would it then become much more declarative? Would we then be able to do much more optimizations than before? I don't think so, and if in addition to that you take into account that declarativity is a relative notion anyway, the claim that it is a declarative language would still be quite valid.

• Jan Hidders