Circular: two mutually circular paramterized attributes
Eval x(a)
Eval y(a)
Eval x(a)
Eval y(a)
x(a) == true: true
Eval y(a)
y(a) == true: true
Eval x(b)
Eval y(b)
Eval x(b)
Eval y(b)
x(b) == true: true
Eval y(b)
y(b) == true: true