  For a given base scheme, a correspondence is established between a class of
sheaves on curves over this base scheme and certain points of infinite
Grassmannians. This equivalence extends to a characterization of commutative
algebras of ordinary differential operators with coefficients in the ring of
formal power series over a given $k$-algebra. Our construction generalizes the
approach of M.Mulase, which gives the above connection in the case that the
base scheme is one closed point.
