  We study the linear space generated by the multigraded Betti diagrams of
Z^n-graded artinian modules of codimension n whose resolutions become pure of a
given type when taking total degrees. We show that the multigraded Betti
diagram of the equivariant resolution constructed by D.Eisenbud, J.Weyman, and
the author, and all its twists, form a basis for this linear space.
