There's another thread going on where the meaning of "theory" is being
discussed.
It put me in mind of an old phrase they used to use among scientists,
namely, "not even wrong".

Jim Gray missing at sea after a Sunday sail to the Farallon Islands.
http://sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/01/30/
BAGGTNR93G1.DTL
Marshall

Abū ʿAbd Allāh Muḥammad ibn Mūsā al-Khwārizmī died in 850 AD,
leaving a significant contribution. He is often called the Father of
Algebra. His publication in 825 of "On the Calculation with Hindu
Numerals" was a significant industry milestone. Its translation into

Consider the following relation
   person(P,M,F) :-  person P has mother M, father F.
Suppose M,F are non-nullable foreign keys with enforced referential
integrity back into the person relation.   By induction a non-empty

Does someone know where I can learn more about Universal Quantifier
(Predicate logica) in relation with Database design.
Any help is welcome.
Paul from Holland.

I agree with the saying "go to the source". So I did. I do database
programming for a living. And I want to know what else is out there,
that is based in formal methods. I just hear that there is all this
great research already done and we are not using it.

Scanning through the archives to see what people had said about
continous time I found this from way back in July 2004:
Marshall Spight wrote:

Just a quickie.
Would one be correct in saying that "a key represents the set of
antecedents of the material implication in a relation's predicate?".
I have always considered keys in terms of functional

One feature of some ERP and other software application systems is the
ability for the customer site to indicate in the setup which attributes
are required and which are not related to the various data entry
"screens."  So, customer A might consider birthdate to be a required

All,
I have just discovered, thanks to this group, the book "Developing
Time-Oriented Database Applications in SQL" by Richard T. Snodgrass
which certainly seems to be an excellent reference on the subject of

Hi.  I'd like to know when it is appropriate to use an integer and when
to just use the text. For example, I have a database here which
represents input to an application.  One table Input stores many
records each of which corresponds to a "block" (doesn't matter what

Apparently the following four algebraic properties (or something
similar) are considered important, possibly showing an approach is
well-grounded in mathematics.
Commutative:  A and B = B and A

Consider a scenario in which various users must be stored in a
relational database. Said users have different access levels. In
addition, each type of user has different information associated with
their account. Here's an example:

I have some thoughts on how best to achieve concurrency in an RDB.  You
may want to keep in mind that I am a "systems programmer" with
little experience in using an RDB.  I'm posting to this newsgroup to
see whether my ideas have a reasonable basis.

Here is a partial formalization of a relational algebra based on MV
attributes.  The approach appears simple and intuitive.  In particular
the join of two relations is rather elegant.
Definition:  An attribute a consists of an attribute-name N(a) and a