Re: About grammar and syntax on a possible relational language

On Mar 12, 4:29 pm, TroyK <cs_tr..._at_juno.com> wrote:
> On Mar 12, 8:33 am, Cimode <cim..._at_hotmail.com> wrote:
>
>
>
> > On Mar 11, 5:38 pm, Cimode <cim..._at_hotmail.com> wrote:
>
> > > > Why not:
> > > > [MAKE RICH_EMPLOYEE = {EMPLOYEE WITH SALARY > 100000}]
> > > > (with curly braces around the derivation expression)? It seems a
> > > > little "off" to use them only sometimes.
>
> > > Because I reserved '[]' to relation operation and '{}' to relation
> > > definition. I will keep the remark in mind though
>
> > To be more explicit {} is attribute level manipulation and [] is
> > relation level manipulation to keep the language as versatile as
> > possible. For example
>
> > [MAKE R0 = {ATTRIBUTE0_1, ATTRIBUTE0_2}]
> > [MAKE R1 = {ATTRIBUTE1_1, ATTRIBUTE1_2}]
> > [MAKE R2 = R0 UNION R1]
> > PRESENT2D [R2]
>
> > does the same thing as
>
> > PRESENT2D [{ATTRIBUTE0_1, ATTRIBUTE0_2} UNION {ATTRIBUTE1_1,
> > ATTRIBUTE1_2}]
>
> > It is also about the coherence of the computing model behind. The
> > input of the media layer is necessarily a relation. The input of the
> > logical layer may either be a relation or an attribute set.
>
> I see what you're aiming for and I think that I agree with the syntax.
> The example that introduced the confusion for me is this:
> [MAKE VIP_MEMBER = {RICH_EMPLOYEE}]
>
> where "RICH_EMPLOYEE" refers to a relation.
Yes, under this premise a relation is a synonym for type.

> TroyK
Received on Wed Mar 12 2008 - 17:36:42 CET