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<<What's the substantial difference with repect to 'dimensionality' ?>>
Mainly that SQL current implementation are direct image implementation
which limits their ability to represent relvar adequately. They can
only manipulate relvar on a representation per representation basis.
<<See above, and what analogy do you have in mind ?>>Please read above. A ruby's cube has 3 dimensions (width, length, depth). When you look at one face of the cube you see only 2 dimensions. These 2 dimensions are on possible representation of the cube.
vc wrote:
> Cimode wrote:
> > Thank you for your feedback.
> >
> > << This does not make any sense, the dimension of a relvar is the
> > number
> > of attributes.>>Absolutely. but SQL table implementations are not
> > relvar, just a possible representation of a relvar. Commonly
> > implemented SQL DBMS Tables are bidimensional.
>
> VAR CUBE RELATION { X REAL, Y REAL, Z REAL}
>
> TABLE CUBE(X REAL, Y REAL, Z REAL)
>
> What's the substantial difference with repect to 'dimensionality' ?
>
> > <<I suppose that you know how to represent a cube with a table.>> It is
> > an analogy used for communication's sake. You misread and
> > misunderstood my comment. I said that a face of a cube is
> > bidimensional and is a comparable to what a SQL Table is to a relvar.
> > (the relvar being a 3 dimensional relvar). This analogy has been used
> > by DATE and PASCAL and I find it very valid.
>
> See above, and what analogy do you have in mind ?
Received on Sat Jun 03 2006 - 09:37:00 CDT