Re: algebra equations for Reference and FD constraints


"paul c" <toledobythesea@xxxxxxxx> wrote in message
news:lts4l.4362$hr3.935@xxxxxxxxxxxxxxx
Brian Selzer wrote:
...
Second, this does not dispel the claim that there are some 'model'
concepts that can't be expressed with the algebra or calculus. In
particular, database updates cannot be expressed. To be sure, a value
that is to be assigned can, but the update itself--the actual
assignment--cannot. Nor should it.

"update" is not a relational model concept nor is "assignment". They are
both programming language concepts and are not necessarily present
depending on the language, eg., some languages don't need assignment. Same
goes for variables, aka pointers. Imputing any of these concepts to the
relational model is making the same illogical mistake as criticizing the
RM because of flaws in the SQL language. The mistake originates with the
false assumption that a dbms implementation that may have been partly
inspired by Codd's original model can somehow introduce or retro-fit
concepts to that model, that he never ascribed to it. The mistake is
mysticism at its finest. Whereas I would say that if one can't express a
concept with either an algebra or calculus, then the concept is not a
'model' concept in the first place.


The Relational Model as Codd defined it involves what he called
'time-varying relations.' These are not the static relations that are the
result of algebraic expressions--though their values at any particular point
in time are. Your statement that neither 'update' nor 'assignment' are
relational model concepts is patently absurd, for how can a relation vary
with time unless there is some form of update or assignment involved.

<snipped irrelevant references to SQL>


.

Relevant Pages

  • Re: algebra equations for Reference and FD constraints
    ... both programming language concepts and are not necessarily present depending on the language, eg., some languages don't need assignment. ... Imputing any of these concepts to the relational model is making the same illogical mistake as criticizing the RM because of flaws in the SQL language. ... Whereas I would say that if one can't express a concept with either an algebra or calculus, then the concept is not a 'model' concept in the first place. ... Your statement that neither 'update' nor 'assignment' are relational model concepts is patently absurd, for how can a relation vary with time unless there is some form of update or assignment involved. ...
    (comp.databases.theory)
  • Re: algebra equations for Reference and FD constraints
    ... concepts that can't be expressed with the algebra or calculus. ... depending on the language, eg., some languages don't need assignment. ... The Relational Model as Codd defined it involves what he called ... If the database is supposed to reflect what is the case, ...
    (comp.databases.theory)
  • Re: Relational model versus object model
    ... > Every now and then, a question pops-up on this forum, that initiates ... > the discussion on how the relational model relates to the object ... > Handling redundancy by hand is not fun (and programming is supposed to ... > one of the language you work in, ...
    (comp.object)
  • Re: Databinding - Best Practice (object-oriented)
    ... >> decent database theory introductory book. ... >relational model throughout your application severely restricts the ... >inheritance, interfaces). ... IMO a good OO language must have relational features and a good ...
    (microsoft.public.dotnet.framework.windowsforms.databinding)
  • Re: Databinding - Best Practice (object-oriented)
    ... >> decent database theory introductory book. ... >relational model throughout your application severely restricts the ... >inheritance, interfaces). ... IMO a good OO language must have relational features and a good ...
    (microsoft.public.dotnet.framework.windowsforms)