# Re: Onto a potential relational manipulation language

Date: Sat, 13 Dec 2008 01:17:34 -0800 (PST)

Message-ID: <40467a41-410a-4d67-a5ca-222765fc2b34_at_f24g2000vbf.googlegroups.com>

On 12 déc, 19:58, paul c <toledobythe..._at_oohay.ac> wrote:

*> vadim..._at_gmail.com wrote:
**>
**> ...
**>
*

> > There is established Logic <-> Algebra correspondence. For

*> > propositional calculus we have boolean algebra. What algebra do we
**> > have for predicate calculus? None. I'd suggest that RL is predicate
**> > calculus without quantifiers and relation attributes.
**> > ...
**>
**> Hold on, Vadim! Regarding quantification, I thought Codd's algebra
**> included analogies for Exists and Forall in the projection (fundamental,
**> can't be defined in terms of the other fundamental ops, ie., REMOVE,
**> NAND or NOR, and TCLOSE) and division (defineable in terms of the other
**> ops). Same must be so of D&D A-algebra. If so, RL must at least have
**> quantification since it has a form of projection in its lattice union.
**> If I've got all that right, there must be a way to express Forall in RL
**> with some syntax or other. Am I distorting the situation?
**>
**> (BTW, the thing I like (given my small knowleCone names the attributes
**> to be projected and the ones that are 'removed' are implicitly the
**> header minus the named ones. But if projection has two operands, it
**> opens the door for perhaps more exotic structures, such as the
**> "multi-relations" Darwen has written about lately (note I'm not saying
**> that he advocates them just because he's written about them), where
**> tuples in the same structure can have different attributes. I gather
**> part of the motivation behind multi-relations is to help deal with
**> so-called "missing information", whereas my attitude so far is that it
**> could just as easily be a way for one structure to allow multiple
**> predicates, which might give some programming leverage, eg., allowing
**> multiple predicate references, even updates in a single structure
**> reference.)
*

Precisely. One can hardly implement a satifactory solution to missing
information through decomposition without a computing model that does
implement combinatory analysis between domains of un-ary relations
that constitute multi attribute relations. I somehow suspect this is
orthogonal to the scope of Vadim's remarks.
Received on Sat Dec 13 2008 - 10:17:34 CET