17
Games for
9
MSO
•
Theorem
If duplicator has a winning strategy
for the l,k-Fagin game, then A, B are
indistinguishable in MSO[l, k]
•
•
•
MSO[l,k] = has l second order
9
quantifiers,
followed by
f
2
FO[k]
•
Problem: the game is still hard to play