The DPDD describes (most completely in Section 3.2.1) the execution of forced and precovery photomery during prompt processing. Footnote 26 says that the DPDD treats them as "just" DIASources that may be flagged appropriately in the DIASource table or stored in a separate table. This statement creates some ambiguity I'd like to resolve.
Because DIAForcedSources and DIASources have different semantic meanings, I'd first like to propose that we distinguish them explicitly in the DPDD (even if the actual storage of DIAForcedSources turns out to be as a flagged subset within the DIASource table). This would eliminate footnote 26, which is itself inconsistent with the statement in Section 3.3.1 that the DIASource table is "a table of sources detected at SNR > 5 on difference images." In my scan of the rest of the DPDD, actual usage of "DIASource" appears to be restricted to "unforced" DIASources, contra footnote 26.
I propose that we further create a DIAForcedSources table that clarifies which columns will be present in that table. I believe these should be at least:
diaForcedSourceId, ccdVisitId, diaObjectId, psFlux, psFluxErr (which is missing from DIASource!), flags.
I also think we should include totFlux and totFluxErr (forced flux on the PVI): these are required to reconstruct the DC lightcurve of variable stars when the difference image magnitude is near that of the template.
I also suggest we state explicitly that any existing DIAForcedSources already in the PPDB will be included in alert packets with the 12-month DIASource history. When available, these measurements are obviously more valuable to end-users than the upper limits provided by
Finally, I suggest that we clarify that DIAObject timeseries features are computed on DIASources only and not DIAForcedSources (even if present), since the latter have complex sampling histories related to the precovery window and in many cases will be nondetections.