Re: About grammar and syntax on a possible relational language

On Mar 12, 8:33 am, Cimode <cim...@xxxxxxxxxxx> wrote:
On Mar 11, 5:38 pm, Cimode <cim...@xxxxxxxxxxx> 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.

TroyK
.

Relevant Pages