7
Simultaneous Fixpoints
•
U
1
, U
2
, …, U
k
= finite sets
•
Definition
Let F : P(U
1
)
£
…
£
P(U
k
)
!
P(U
1
)
£
…
£
P(U
k
).
A fixpoint for F is
X = (X
1
, …, X
k
), X
1
µ
U
1
, …, X
k
µ
U
k
s.t. F(X) = X
•
•
lfp
(F),
ifp
(F),
pfp
(F)
defined as before
•