What to call this operator?
Date: 26 Jun 2005 20:27:15 -0700
Message-ID: <1119842835.425835.266500_at_f14g2000cwb.googlegroups.com>
In chapter 4 or The Third Manifesto, D&D define a "new relational algebra."
This algebra includes two operations named "<AND>" and "<OR>". (They use some weird triangle characters which I'm approximating with <>.)
Given relations S and T, having sets of attributes a (only in S),
b (in both S and T) and c (only in T), they define:
<AND> as { (a, b, c) | (a, b) in S, (b, c) in T }
<OR> as { (a, b, c) | (a, b) in S, c unconstrained UNION
(a, b, c) | (b, c) in T, a unconstrained }
"unconstrained" means that all values from the domain are present.
They go on to point out that <AND> is the natural join, but they don't give a name to <OR>.
Does anyone have a good idea for what it should be called? I don't like "or" because it's ambiguous with the boolean operator. "<OR>" isn't great for syntactic reasons. "Disjunction" is cumbersome. I'd like to hear something analogous to "join." What about "meet", does that work? It's the usual counterpart to "join" but I don't know enough math to decide if it's appropriate.
Marshall Received on Mon Jun 27 2005 - 05:27:15 CEST