I was discussing study data transformation with someone (think SDTM data transformed to ADAM data).
Here is another issue for the group to discuss:
To capture raw data as well as "for analysis" transformed data - I propose to use the same table (e.g., measurement) and use type columns to indicate raw vs. transformed. (just to put a proposal to the discussion)
Not capturing raw data is probably not an option. This would make OMOP inferior to current standards.
To capture transformation steps (captured in Define.XML), OMOP METADATA table could be used for that purpose.