A simple notation, again

From: David Cressey <cressey73_at_verizon.net>
Date: Mon, 16 Jul 2007 14:15:48 GMT
Message-ID: <o4Lmi.4051$fj5.2089@trnddc08>

Using the notation [A B C] for <NOT> (A <AND> B <AND> C), etc.

The following [ A [B]] means "A implies B" for Boolean algebra. What is the corresponding thing for Relational Algebra?

Also, I'm trying to come up with a bracket notation for a "literal relation", like literals for simple datatypes like numbers and character strings.

I'm toying with this:

[["David"  "Cressey" 1]

["Marshall" "Spight" 2]
["Bob" "Badour" 3]
["Jan" Hidders" 4]]

This would represent a relation of order 3 and cardinality 4.

What I don't like about this is that the binding between attribute values and attribute names is
by position rather than by name, and in fact the attribute names don't even appear here. That's unacceptably bad. The symmetry is appealing, but it clearly needs improvement.

Does tutorial D have a way of laying out a relation as an explicit literal character string? Received on Mon Jul 16 2007 - 09:15:48 CDT