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Re: Possible bridges between OO programming proponents and relational model

From: Cimode <cimode_at_hotmail.com>
Date: 3 Jun 2006 06:27:53 -0700
Message-ID: <1149341273.193104.134790@y43g2000cwc.googlegroups.com>


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.

<< The only way to do this is to force all logical tables to have two  attributes.>>Why is that? What sources makes you believe that? (Curious about that assertion) Are you refering to Transrelational Model?

<<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.

<<Are you suggesting that the memory is less physical than the disk?>>Interesting question but the answer is obviously no. The argument here is about getting better independence *progressively* through thinking as to how in-memory representation of relvar could be more truthful to what a relvar . The question is whether OO in-memory mechanisms could support such effort. And how?

Alfredo Novoa wrote:
> Cimode ha escrito:
>
> > One of the main current flaws of current SQL DBMS systems is their
> > incapability to implement the multidimensionality of relvars.
>
> This does not make any sense, the dimension of a relvar is the number
> of attributes.
>
> > The main
> > reason seems to be the lack of independence between the physical layer
> > and logical layer the represent the data. In several DBMS tuples are
> > right away on disk projections imposing that all tables are considered
> > bidimensional.
>
> The only way to do this is to force all logical tables to have two
> attributes.
>
> > In fact, it should not be the case because a
> > bidimensional RTable is only a *representation* of some entity. An
> > interesting analogy that may help communication, is Rubi's Cube (3
> > dimensional): looking at one face of the cube it's only one possible
> > representation of the cube (being the relvar)
>
> I suppose that you know how to represent a cube with a table.
>
> > some insight (flamers please refrain) onto how OO mechanism may help
> > separate the logical operation (in memory) from physical layer...
>
> Are you suggesting that the memory is less physical than the disk?
>
>
> Regards
> Alfredo
Received on Sat Jun 03 2006 - 08:27:53 CDT

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