Re: views of binary operations

Cimode wrote:
> Aloha Kakuikanu wrote:
> > Marshall wrote:
> > > Aloha Kakuikanu wrote:
> > > > Marshall wrote:
> > > > > Consider named views of binary operations on relations.
> > > > >
> > > > > Given a relational operator "op" and relation variables A and B,
> > > > > and a declaration of:
> > > > >
> > > > > r = A op B
> > > > >
> > > > > the language evaluates the expression "A op B" and assigns the
> > > > > result to r.
> > > > >
> > > > > However, if we declare this as a view, ...
> > > >
> > > > View is a named expression. r is a view.
> > >
> > > Is it necessarily named? Might we find use for an anonymous view?
> >
> > Well, the point is that the term "view" is redundant and SQL-ish.
> > Relations and relational expressions are the fundamental concepts, and
> > view is some bastardized idea.
> I agree. I would go one step further to deal with Marshall's question
> not use the term *view* at all. As I have said, anything related to
> SQL is one way or another a source of confusion when dealing with RM
> issues.

Views and snapshots aren't unique to SQL. They're fundamental to relational.

A simple rule of thumb might be this: A view is an expression, unevaluated, while an assignment necessarily requires a value, thus a snapshot. Special syntax is needed to differentiate a view creation ("view(r) = A op B" or perhaps "view r = A op B") from a simple assignment of a relval to a relvar ("r = A op B"). Received on Mon Jul 17 2006 - 13:56:26 CEST