Erratum: A Topological Relational Algebra in Lisp
From: Norbert_Paul <norbertpauls_spambin_at_yahoo.com>
Date: Sat, 24 Jan 2015 18:11:35 +0100
Message-ID: <ma0jn7$n74$1_at_dont-email.me>
Date: Sat, 24 Jan 2015 18:11:35 +0100
Message-ID: <ma0jn7$n74$1_at_dont-email.me>
Norbert_Paul wrote:
> The initial case gives:
> R1 = { (a,b) in X x X | g1(a) R+ g1(b)) }
> R2 = { (a,b) in X x X | g2(a) R+ g2(b)) }
> R3 = { (a,b) in X x X | g3(a) R+ g3(b)) }
> Then a result relation is Rz = R1 /\ R /\ R3 (where /\ is set
> intersection).
YA error: This must be
R1 = { (a,b) in X x X | g1(a) R^* g1(b)) }
R2 = { (a,b) in X x X | g2(a) R^* g2(b)) }
R3 = { (a,b) in X x X | g3(a) R^* g3(b)) }
Where R^* is the transitive and reflexive closure of R.
Received on Sat Jan 24 2015 - 18:11:35 CET