WebAPI doesn’t use the cdm’s cohort tables. The cohort generation tables were discussed here:
One of the reasons we don’t use the CDM’s table, is that the cohort definition table doesn’t include the level of detail that we’d need for authoring cohort definitions. Another is that people usually lock down their CDM tables such that they are read-only. So, we introduced a ‘results’ schema, and you’ll find a ‘cohort’ table in that schema, and the results chema is for read/write access.
The topic of the cohort and cohort_definition table has caused too much confusion, and I’m wondering if those tables used by webapi should be renamed.