 This approach is taken by Bacchus (1990) and Halpern (1990), corresponding to the idea that selections are independent and with replacements. With these semantics the example above can be formalized as \(Px,y (B(x) \wedge \neg B(y))= 20/81\). There are also more general approaches to extending the measure on the domain to tuples from the domain such as by Hoover (1978) and Keisler (1985).