Re: Guessing?

From: David BL <>
Date: Tue, 27 May 2008 22:45:05 -0700 (PDT)
Message-ID: <>

On May 27, 4:46 am, paul c <toledoby..._at_ac.ooyah> wrote:
> Brian Selzer wrote:
> > "paul c" <toledoby..._at_ac.ooyah> wrote in message
> >news:09p_j.294813$pM4.94170_at_pd7urf1no...
> ...
> >> It is becoming more and more apparent to me that the Assignment Principle
> >> is a case of wanting to have your cake and eat it too.
> > In my opinion the Assignment Principle is more important than being able to
> > update views that shouldn't be updatable. If you issue an update, and are
> > informed that it succeeded, then you should be able to expect that what you
> > changed actually changed. For example, if I insert a row, and the insert
> > succeeds, then when I re-read the row, I should be able to determine whether
> > another user changed it by simply comparing the values I inserted to the
> > ones read out: if they're different or nonexistent, then someone else
> > changed or deleted it.
> > ...
> Sorry, slip of the keyboard, I didn't mean to mention the Assignment
> Principle (which is okay by me) rather what I remember being called the
> Principle of Interchangeability. The latter sounds wise, accepting and
> maybe even politically correct in some circles but I do think it is
> wishful thinking and suspect it is founded on quicksand.
> Regarding the Assignment Principle, I say that in this case it is not
> violated, assuming we are talking about relational algebra that is closed.

Are you saying the Assignment Principle isn't violated assuming the mutual exclusion integrity constraint causes the attempted update to the virtual relvar to fail with an error? Received on Wed May 28 2008 - 07:45:05 CEST

Original text of this message