Re: About grammar and syntax on a possible relational language

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 [{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. Received on Wed Mar 12 2008 - 15:33:09 CET