Re: On view updating

Costin Cozianu <c_cozianu_at_hotmail.com> writes:

> I think they've got it wrong on several counts.
>
> 1) Is whether view updating is crucial to "logical data independence".
>
> Very little have I seen in the way of defending this point. Since
> relvars are "variables" and the rest are computed values, and Date
> insists so much on the logical distinction between variabke and values,
> well we should apply a rather trivial distinction
>
> that rvalues are not lvalues.
>
> By insisting that views should be seen as updatable Date actually
> insists that in his model some values should be used as lvalue.

This had occurred to me, also. Treating views as writable introduces forms of indirection and aliasing which Date and Darwen otherwise take great pains to avoid in The Third Manifesto.

I'm of two minds on the topic. Although I agree that writable views are not crucial to logical data independence overall, they can certainly help isolate individual pieces of an application from details of the schema. On the other hand, I can see advantages in program clarity if application code always deals directly with base schema during writes. Regardless, the issue doesn't seem fundamental to the relational model in any way. Received on Mon Sep 20 2004 - 03:58:43 CEST