observed criterion

[CV-GPhL]

I find the whole concept of "observed criterion" confusing and unnecessary. What are we trying to describe here? When is the last time anyone in MX applied some individual, per-reflection criteria a la

• _pdbx_diffrn_merge_stat.observed_criterion_I_max (The criterion used to classify a reflection as 'observed' expressed as an upper limit for the value of I.)
• _pdbx_diffrn_merge_stat.observed_criterion_I_min (The criterion used to classify a reflection as 'observed' expressed as a lower limit for the value of I.)
• _pdbx_diffrn_merge_stat.observed_criterion_sigma_I (The criterion used to classify a reflection as 'observed' expressed as a multiple of the value of sigma(I).)

The only place where some programs/users might apply such a criteria could be during refinement itself (or maybe in computing some R-values):.

Unfortunately, the "observed_criterion" is defined in the _reflns category, suggesting that any selection process was done within the reflection data prior to refinement. Of course, multiple selection processes happened during data-collection, but none as simplistic as an I>sig(I) cut-off or a Imax/Imin limit. These selection processes are highly program and processing-step specific (as well as depending on program versions and run-time parameters) and can be very difficult to capture in anything machine readable.

Of course, we could just define those criteria in a way that would catch all reflections in any case. But this would mean that

• _pdbx_diffrn_merge_stat.number_obs
• _pdbx_diffrn_merge_stat.number_all
  would always have the same value ... not sure that is useful here? I would leave any distinction between the _all and _obs quantities out completely and just stick with reflections contributing to this data set.