Re: Relational lattice

How about small counter example?

Consider

R=

x y
- -

1 2
2 2
2 3
3 3

I suggest that

X = X12 join X34 join X56

where

X12=

x y
- -

1 2
2 2
2 3
3 3
3 2

X34=

x y
- -

1 2
2 2
2 3
3 3
3 2
1 3

X56=

x y
- -

1 3

is a solution that meets conditions 1-4. (The fact that x5=1 and x6=3 is the only pair is especially handy when checking the above conditions). Received on Mon Mar 14 2005 - 17:50:29 CST