P(?) and N(*) in datto

The datto example in the overview of interfamily ops uses this P(?) syntax and i’m just wondering what that is doing. If i only use P I get a warning about block 0 missing

The parameter refers to DAT columns by names. The ‘?’ symbols is a pattern to match any single character. In this case P(0), P(1) and P(2) columns (see Pattern Matching - Derivative).

DATs don’t have Attributes like POPs do.