Not exactly, the functional core/imperative shell paradigm has nothing to do with the data model/business logic distinction. It’s used in functional languages t

Not exactly, the functional core/imperative shell paradigm has nothing to do with the data model/business logic distinction. It’s used in functional languages to create an imperative boundary with the real world and its side effects. For example in the functional core you’ll have no nulls and all the business objects are valid. In the imperative shell that interfaces with the real world you validate all the inputs, build your valid objects and handle all the external error conditions.