# Relational Calculus, which subset of FOL is supported

From: tbeer <thomas.o.beer_at_gmail.com>

Date: Fri, 11 Jul 2008 06:54:43 -0700 (PDT)

Message-ID: <5d71c9c4-8a72-4938-bb4c-5a4bb511de7a_at_c58g2000hsc.googlegroups.com>

Hi all!

Date: Fri, 11 Jul 2008 06:54:43 -0700 (PDT)

Message-ID: <5d71c9c4-8a72-4938-bb4c-5a4bb511de7a_at_c58g2000hsc.googlegroups.com>

Hi all!

It is often stated that relational calculus (tuple domain calculus) is
a subset of first order logic.

In the dbforum, wikipedia, wapedia articles:

*- http://en.wikipedia.org/wiki/Relational_algebra
*

- http://wapedia.mobi/en/Relational_algebra
- http://www.dbforums.com/archive/index.php/t-424876.html it is claimed that: 1) "Codd's algebra is not in fact complete with respect to first-order logic, he restricted the operands to finite relations only and also proposed restricted support for negation (NOT) and disjunction (OR)" 2) "Relational algebra actually corresponds to a subset of first-order logic that is Horn clauses without recursion and negation." 3) ">What is the relation between the relational model and first oder logic? They are one and the same."

Which "subset" of FOL is supported by the relational calculus in
detail?

I know Codd's (original) paper from 1970 (unfortunately I don't have
the original one from 1969), but I wasn't able to find an answer to my
question.

I'm looking for a more "serious comparison" of relational algebra (or relational calculus) and FOL (or predicate logic in general), i.e. expressive power, limitations, etc.

I really appreciate your help.

Best regards,

Tom
Received on Fri Jul 11 2008 - 15:54:43 CEST