The status of a reflection related to _refln.pdbx_signal.
A measured reflection counts as observed if:
_refln.pdbx_signal >= _reflns.pdbx_observed_signal_threshold
and unobserved if:
_refln.pdbx_signal < _reflns.pdbx_observed_signal_threshold
An unmeasured but observable reflection is one that has not
been measured, but the data processing has determined that it
would have been expected to be observed had it been measured.
An unmeasured and unobservable reflection is one that the data
processing has determined would not have been expected to be
In datasets in which _refln.pdbx_signal has been populated, a null
(?) value for this item indicates an unmeasured reflection for
which it is not known whether it is observable or not.