Documenting protocols and variants of a single trait

For traits such as NDVI or specific leaf area, multiple methods may be used in a single dataset. This suggests that the IDD needs to accommodate:
1. Descriptions of how a specific variable was measured.
2. Variants of a single variable.
My suggestion is to include a new category Protocols under Dataset and define variables for documenting protocols. To handle variants of a single variable, the easiest approach would be to add a suffix with a number. For example, NDVI variants might be NDVI_01, NDVI_02 ... For a studying comparing methods, we might have more than nine variants, so I'd keep the leading 0.