•We have NP = 9 SO, coNP = 8 SO
•If we prove 9 SO ¹ 8 SO then P ¹ NP
•
•Definition. MSO = Monadic
SO
(restrict quantifiers to unary
relations)
•
•Definition. Monadic NP = 9MSO;
Monadic coNP = 8MSO
•
•[give examples of
NP-complete problems in monadic NP]