Every semifinite von Neumann
algebra A possesses an expectation ♮ : A → W, where W is a commutative von
Neumann subalgebra of A containing the center of A, and where ♮ extends the
trace of a “large” finite subalgebra of A. An AW∗-algebraic proof yields
applications to the embedding of semifinite AW∗-algebras in algebras of type
I.