 One needs to choose a half of the fluxes to quantize, or a "polarization" in the geometric quantization-inspired language of Diaconescu, Moore, and Witten and later of .Alternately one may use the K-theory of a 9-dimensional time slice as has been done by .In the classical limit of type II string theory, which is type II supergravity, the Ramond–Ramond field strengths are differential forms.