# Re: Extending my question. Was: The relational model and relational algebra - why did SQL become the industry standard?

Date: Thu, 27 Feb 2003 00:46:25 -0500

Message-ID: <b3k8ks$kca$1_at_slb5.atl.mindspring.net>

Paul Vernon wrote:

*>Humm. I think I can counter my argument:
**>
**>TYPE TINY_INT POSREP( {-1,0,1 } );
**>
**>TYPE TINY_PI
***>POSREP( {-1.5 PI, -1 PI, -.5 PI, 0 PI, 0.5 PI, 1 PI, 1.5 PI, 2 PI } );
**

*>*

*>TYPE TINY_R2 POSREP( { 0 SQRT2, 1 SQRT2 } );**>*

*>TYPE TINY_POINT*

*>POSREP POINT_XY (X TINY_INT, Y TINY_INT)*

*>POSREP POINT_RT (R TINY_R2, T TINY_PI*

*> CONSTRAINT IF R = 0 SQRT2 THEN T = 0 PI );**>*

*>Now both poss reps are equivalent, so this is a well constructed type and as*

*>such not a bad example of a type with more than one possible representation.*

*>*

*>:-)*

*>*

*>Regards*

*>Paul Vernon*

*>Business Intelligence, IBM Global Services*

*>*

*>*

*>*

I'm lost on who is countering whose argument here, but you have described one type that represents the 9 points on and at the center of the 2 x 2 square at the origin of Z x Z, and another type that represents 9 points on and at the center of a circle (I think you may have meant to allow -0.75PI, ..., 0.75PI, 1 PI), instead of twice these values).

SK

*>
**>
*

Received on Thu Feb 27 2003 - 06:46:25 CET