Re: A different definition of MINUS, Part 3

On 19 déc, 20:54, paul c <toledobythe...@xxxxxxxx> wrote:
Cimode wrote:
On 19 déc, 19:37, paul c <toledobythe...@xxxxxxxx> wrote:
Cimode wrote:
[Snipped example]
<<As soon as they started
making premises, they lost me because it doesn't look like their
method is anything more than case analysis that have any chances to
be
scaled up to practical problems. >>
Precisely.  I would go further as to say that hoping that using solely
algebra would be sufficient to achieve such resultis nothing more than
the holy graal of RL.  As you mentionned in an earlier post, the
example of lack of quantifiersi is one major obstacle most current
DandD work seem to ignore without consequence or awareness of the
price to pay.
Regards.. .
I think around 1972 Codd wrote a proof that the algebra was logically
equivalent to FOPC, later others (I forget their names) corrected a few
errors and proved the equivalence.  This is why I'm happy to try to show
things with the algebra, even though it can be tedious trying to see the
forest for the trees.

To my knowledge, Codd never mentionned that FOPC would be sufficient
to clarify RL.  Choosing to work *solely* on that angle is a matter of
personal choice.

Regards...

I don't think that's what I said.  I think Codd meant that his
relational model obeyed (ie., is based on) both of FOPC and his algebra
Codd never, to my knowledge, closed the door in claiming that FOPC or
algebra would be a sufficient tool to clarify all aspects or RL. By
binding algebra to FOPC, he simply opened the door to an entire
spectrum of investigations that could involve not only algebrical
concepts but also non-algebrical concepts that can be expressed at
some point through algebra. I explain Codd's choice of algebra to
clarify FOPC as a choice for the expressive power of algebra as
opposed to other mathematical tools.

  The personal choice is whether one uses algebra or fopc not only to
understand his model but to define it.
or to redicover it and seeing the limits of the initial formulation
(any great theory does have its limits). RL existed much before being
expressed and clarified by Codd's algebra. Choosing to close that
possibility is not what Codd had in mind when he opened the door. The
fact that RL was immediately bound todatabase theory was purely a
circumstancial fact. It is not hard to imagine that had Codd being a
network engineer working at IBM that did not have to deal with IMS and
MVS datasets problems, the relational model would now be predominant
in solving traffic problems.

Above this minor point, I find it very frustrating that relational
algebra as expressed by D&D is somehow coming to the same pitfalls,
it tried once to get around. Crumbling under its own weight of
ineffective and redundant semantics and rules, it does not serve the
primary purpose of the RM anymore: the usefulness of solving computing
problems by setting a more effective conceptual model that avoids the
pitfalls of the hierarchical an dnetwork model.

That is a fact, ra theorist will have hard time accepting in
subjecting their certainties to scrutiny of math .

This is one of these moments where I wish Codd would be here to answer
so many questions.

Regards...
.

Relevant Pages

  • Re: OT: SQL
    ... (SQL is something between an algebra and a calculus; ... Some of your ideas are just wrong: "Codd et. al. never ... and advocated against nested relations ... as part of a dbms is so spectacularly bad I am speechless. ...
    (sci.logic)
  • Re: A different definition of MINUS, Part 3
    ... DandD work seem to ignore without consequence or awareness of the ... I think around 1972 Codd wrote a proof that the algebra was logically ... Codd never mentionned that FOPC would be sufficient ...
    (comp.databases.theory)
  • Re: A different definition of MINUS, Part 3
    ... I think around 1972 Codd wrote a proof that the algebra was logically ... I think Codd meant that his relational model obeyed both of FOPC and his algebra. ... The personal choice is whether one uses algebra or fopc not only to understand his model but to define it. ...
    (comp.databases.theory)
  • Re: Nested Sets vs. Nested Intervals
    ... > <<In order to be more specific, would you please elaborate on the RDF ... give a definition of the algebra ?>> ... you did not clarify what you've meant by a "semantic domain" as ...
    (comp.databases.theory)
Loading