  A solution is given to the following problem: how to compute the
multiplicity, or more generally the Hilbert function, at a point on a Schubert
variety in an orthogonal Grassmannian. Standard monomial theory is applied to
translate the problem from geometry to combinatorics. The solution of the
resulting combinatorial problem forms the bulk of the paper. This approach has
been followed earlier to solve the same problem for the Grassmannian and the
symplectic Grassmannian.
  As an application, we present an interpretation of the multiplicity as the
number of non-intersecting lattice paths of a certain kind.
  Taking the Schubert variety to be of a special kind and the point to be the
"identity coset," our problem specializes to a problem about Pfaffian ideals
treatments of which by different methods exist in the literature. Also
available in the literature is a geometric solution when the point is a
"generic singularity."
