Re: A different definition of MINUS, Part 3

On 18 déc, 20:31, Cimode <cim...@xxxxxxxxxxx> wrote:
Hope this will publish adequately...

R-D= R - (R ∩ D) = R-[(RXD) - (R ∆ D)] = R  U R∆D -  RXD

R=[{1},{2},{4}]
D= [{1},{3}]

R-D = [{1},{2},{4}] U [{2}, {3}] - [{1, 1}{1, 2}{1, 4} {3, 1} {3, 2}
{3, 4}]
=[{1}{2}{3}{4}] - [{1, 1}{1, 2}{1, 4} {3, 1} {3, 2}{3, 4}]
=[{1}{2}{3}{4}] - [{1}, {3}]
=[{2}{4}]

To be more precise, I should have written

R-D= R - (R ∩ D) = R-[(RXD) - (R ∆ D)] = R U R∆D - DXR --> Does make
a difference when headers are brought into the equation...

Apologies..
.