  We develop a natural generalization of vector-valued frame theory, we term
operator-valued frame theory, using operator-algebraic methods. This extends
work of the second author and D. Han which can be viewed as the multiplicity
one case and extends to higher multiplicity (e.g., multiframes) their dilation
approach. We prove several results for operator-valued frames concerning their
parametrization, duality, disjointeness, complementarity, and composition and
the relationship between the two types of similarity (left and right) of such
frames. We then apply these notions to prove that the collection of multiframe
generators for the action of a discrete group on a Hilbert space is norm
pathwise-connected precisely when the von Neumann algebra generated by the
right representation of the group has no minimal projections. The proof is
obtained by parametrizing this collection by a class of partial isometries in a
larger von Neumann algebra. In the multiplicity one case this class reduces to
the unitary class which is path-connected in norm, but in the infinite
multiplicity case this class is path connected only in the strong operator
topology and the proof depends on properties of tensor product slice maps.
