              Data items in the PHASING_MIR_DER category record details\
               about individual derivatives used in the phasing of the\
               structure when methods involving isomorphous replacement are\
               involved.\
\
               A derivative in this context does not necessarily equate with\
               a data set; for instance, the same data set could be used to\
               one resolution limit as an isomorphous scatterer and to a\
               different resolution (and with a different sigma cutoff) as an\
               anomalous scatterer. These would be treated as two distinct\
               derivatives, although both derivatives would point to the same\
               data sets via _phasing_MIR_der.der_set_id and\
               _phasing_MIR_der.native_set_id.