5
Example (cont’d)
•
f
=
9
x.
9
y.(x+x=y
Ć
:
9
z(y < z))
•
•
For any vocabulary
s
and
A
2
STRUCT[
s
], if
A’
is any structure over the same universe
and vocabulary
s
<,+
then
(
A
,
A
’)
˛
f
iff EVEN(
A
)