OK. Now I get it. I did see Mitra's presentation. We developed what we call a "generalized data model" (GDM). It can be easily transformed into Sentinel or OMOP. So, in other words, the harmonization comes BEFORE putting the data into OMOP or Sentinel. Then it is a short jump from GDM to those data models. Based on our research, harmonizing data after they have been put into these other data models has important limitations.
The whole reason we did this was to develop a data model for ETL into OMOP. Then we realized that, if we did it the right way, we could have a data model that 1) works fine as it is for our purposes, 2) can be transformed into other data models to take advantage of all of the analytical downstream benefits of those ecosystems. We work with both OMOP and Sentinel data, and this is a much easier way to work (for us). Others may, of course, disagree, or have different ideas.
Preprint available here: https://www.biorxiv.org/content/early/2017/11/10/194597