  Inspired by Okounkov's work [\emph{Selecta Mathematica}, 7(1):57--81, 2001]
which relates KP hierarchy to determinant point process, we establish a
relationship between BKP hierarchy and Pfaffian point process. We prove that
the correlation function of the shifted Schur measures on strict partitions can
be expressed as a Pfaffian of skew symmetric matrix kernel, whose elememts are
certain vacuum expectations of neutral fermions. We further show that the
matrix integrals solution of BKP hierarchy can also induce a certain Pfaffian
point process.
