Re: Lucid statement of the MV vs RM position?

ralphbecket_at_gmail.com wrote:
> A number of people on this group are proponents of
> Pick (MultiValue) DBMS.

I am an advocate of the data model underlying the MV databases. Because fewer dollars have been spent in recent years to put pretty front-ends on these databases, among other things, most of them are dated, however.

> I've been trying to find a
> definition for MultiValue to give me a better handle
> on the arguments MV types often advance against
> the relational model.

You could read my little trilogy of flashcards at

http://www.tincat-group.com/mv/trilogy.html (I have some javascript cleanup to do, but hopfully you can read each sets of cards easily)

> As I understand it, an MV database is a collection
> of files, a file is a collection of records, records in
> a file all have the same structure, a record is indexed
> by a unique key, a record is a collection of fields, a
> field is a collection of (atomic?) values.

pretty close.

> If that is correct, it seems to me that MV is an
> implementation technology and the RM is a logical
> formalism and that to compare the two is to compare
> apples and oranges.

I have been trying to address this in my blog (same domain as above, but select the blog, starting with Is Codd Dead?)

> That said, debate on the topic still goes on and on
> in this group, so I assume I have failed to grasp
> something important about MV.

My points are intended to be more about the lapses in the relational model that are shown up by seeing other models, such as the MV (which is the main alternative with which I have experience).

> Is there a clear,
> *concise* explanation somewhere of (a) a formal
> (preferably set theoretic) model of MV,

No, it has never, as best I can tell, had a formal and definitely not an exclusively set-theoretic model developed. I did include the earliest write-up that anyone I know has found related to the model in one of my blog entries (The LIST of GIRLS, IIRC).

> and (b)
> how integrity constraints are expressed and enforced
> in an MV database?

Yes, that has been discussed in this forum many times. It is a big topic, but the small version is that there is nothing resembling a SQL-DBMS variety of constraints in Pick.

> (On www.pickwiki.com I came across "A formal
> mathematical critique of Relational Theory and its
> MultiValue opposition", which I hoped would be a
> lucid expression of the MV vs RM position, but
> unfortunately it turned out to be just plain wrong
> where it wasn't incoherent.)

I'll have to find that. Thanks. --dawn Received on Thu Apr 20 2006 - 17:01:26 CEST