If in some initial state S0, it is True that
we Know (circumference-circle 8) then our job is to
find ?plan in which it is True that
for some value of ?x we will Know (radius-circle ?x) if the plan is executed.

We have web services:

(Web-Service Circum-Rad)
(Input Circum-Rad circumference-circle)
(Output Circum-Rad area-circle RETURN-Circum-Rad)

(Web-Service Area-Rad)
(Input Area-Rad area-circle)
(Output Area-Rad radius-circle RETURN-Area-Rad)