scheme
MinimalFiniteSet{
P1[
set ] } :
ex
A being
finite set st
(
P1[
A] & ( for
B being
set st
B c= A &
P1[
B] holds
B = A ) )
provided
scheme
RedInd{
F1()
-> non
empty set ,
P1[
set ,
set ],
F2()
-> Relation of
F1() } :
provided
A1:
for
x,
y being
Element of
F1() st
[x,y] in F2() holds
P1[
x,
y]
and A2:
for
x being
Element of
F1() holds
P1[
x,
x]
and A3:
for
x,
y,
z being
Element of
F1() st
P1[
x,
y] &
P1[
y,
z] holds
P1[
x,
z]