Re: Reminder, blatant ad

x wrote:
> "dawn" <dawnwolthuis_at_gmail.com> wrote in message
> news:1139620678.347430.274910_at_g43g2000cwa.googlegroups.com...
>
> > > This is not necessarily true for all such systems but in many of those
> > > the logical and physical model are closely tied together and their
> > > efficiency in fact often depends on this close relationship.
>
> > What is the test for determining whether they are too tightly coupled?
> > What is it that changes (the "physical model" doesn't resonate with me,
> > I want to know what software components would change) that should not
> > require a change in the logical model but does in some non-relational
> > products? I do not recall ever changing the logical data model in any
> > software I have written when a new version of anything was released. I
> > do recall changing COBOL code with a new release of Primos in 1977, but
> > it was not the logical data model for the indexed sequential files that
> > had to change.
>
> Look at Codd 1970 ACM paper.
> He describes various data dependencies:
> - ordering dependence
> - indexing dependence
> - access path dependence
> then he introduce "a relational view of data".

I've read it and I'm sure I'm just being dense on this, but I don't know what it means in practice to a software developer and where I do understand it, I don't have a full understanding of the risk. I'm wondering if the cure is worse than the disease. --dawn Received on Tue Feb 14 2006 - 03:47:02 CET