Oracle FAQ | Your Portal to the Oracle Knowledge Grid |
Home -> Community -> Usenet -> comp.databases.theory -> Re: More on lists and sets
Jan Hidders wrote:
> Mikito Harakiri wrote:
> > Less chatty version:
> > http://arxiv.org/ftp/cs/papers/0603/0603044.pdf
>
> Mikito, do you know if Vadim's axiomatization is complete? I mean, are
> two queries equivalent iff the algebraic identities allow me to rewrite
> one to the other? Or might there still be algebraic identities missing?
Axiomatization of relational algebra -- that was the question you asked on c.d.t back in 2001?
Relational lattice theory is not complete. Many parts still remain informal -- Spight distributivity criteria among them. It could be written formally, but this expression
(A /\ C /\ 00) \/ (B /\ C /\ 00) \/ (A /\ B /\ 00)
= (B /\ 00) \/ (C /\ 00)
==>
A /\ (B \/ C) == (A /\ B) \/ (A /\ C)
doesn't look like a satisfying axiom.
If we just write all what is known so far there would be too many axioms.