Exercise relationalgebra.cnf

Description
To conjunctive normal form

Derivation

(s \/ s /\ s-)~

⇒ relationalgebra.invoverunion

s~ \/ (s /\ s-)~

⇒ relationalgebra.invoverintersect

s~ \/ s~ /\ s-~

⇒ relationalgebra.absorp

s~