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What to call this operator?

From: Marshall Spight <marshall.spight_at_gmail.com>
Date: 26 Jun 2005 20:27:15 -0700
Message-ID: <1119842835.425835.266500@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.

Anyone have any other ideas?

Marshall Received on Sun Jun 26 2005 - 22:27:15 CDT

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