Re: In an RDBMS, what does "Data" mean?
Date: Sun, 13 Jun 2004 13:12:16 -0500
"mAsterdam" <mAsterdam_at_vrijdag.org> wrote in message
> Dawn M. Wolthuis wrote:
> "x" wrote:
> >>>So if I put my data into an MV database I can access it as if it were
> >>>an RDBMS. However, the converse is not true.
> >>So all data in a MV database can be represented in relational model,
> >>but not all data in a RDBMS can be represented in MV model :-)
> >>Which one is more expressive ? :-)
> > Easy question --
> > if each model can provide a solution for a particular area so that we
> > both an MV and a SQL-DBMS solution and
> > if we can look at the MV model as relational when we choose to do so
> > is usually for the purpose of using SQL against it)
> > but we cannot take the relational model and view the MV model from it
> > Then clearly the more expressive language is ... NOT the one that loses
> > ability to view the data in some other way, right? --dawn
> So now we have language R and language M.
A business problem is brought to people who encode a solution in R and in M. They make the usual design tradeoffs based on whichever implementation they are doing. The M solution can toggle to show you an R view of the solution, but the R solution does not have the ability to show an alternate M view of the solution. Now, you could design an R solution that does permit you to view it as this M solution, but you would have to have decided in advance to do that, otherwise it is likely you will make design decisions that rule out getting back to the original M solution.
> R 'loses the ability to view the data' from within M and that
> would somehow mean M is *more* expressive?
> The only way I could make sense out of that is
> if the (appearant) excess expressions in R could
> *not* be relevant to a solution.
> Do you have an indication as to what those excess expressions are?
> Which statements can you make in R but not in M - IOW
> of which data does R lose 'the abitlity to view the data in some other
Sorry 'bout that. --dawn Received on Sun Jun 13 2004 - 20:12:16 CEST