Re: Sets and Lists, again

Gene Wirchenko wrote:
> On 22 May 2006 17:49:21 -0700, "dawn" <dawnwolthuis_at_gmail.com> wrote:
> >>
> >> Indexes are physical, not logical.
> >
> >No. I am using the term as an index of an array. Array[n] where n is
> >the index. If there is a list in a DBMS named emailAddresses, then the
> >3rd element of that array is (logically) emailAddresses[2] (or [3],
> >depending on the implementation of Arrays) and '2' (or '3') is the
> >value of the index for that element.
>
> Since you are discussing implementation, it is physical.

"Index" has more than one meaning. Yes, "index" in the context of CREATE INDEX is physical, but that is not what is being discussed here.

If you have, say, a list of email addresses to send a notification to, with the order determining which ones to try, in order, until successful delivery, then the order is part of the logical model. The fact that this list can be physically represented as an ArrayList or a LinkedList without affecting the logical model makes it even more apparent that the order here is logical.

Marshall Received on Tue May 23 2006 - 19:12:40 CEST