I am going to bring this to the CDM WG, but wanted to reach out to the community for input first.
The concept_class_id is a required field in the Concept table, found here. However, the concept's class comes from the vocabulary of the concept. What do others put in this field for their custom concepts? We haven't put anything in this field because the custom concepts come from custom vocabularies and a class isn't obvious. And I can't think of a way to make this field valuable for us since these custom concepts are mapped to standard concepts that contain the necessary concept_class_id. What do others do? Without a way to add value, I would like to propose that this field is changed to "optional" instead of putting garbage/useless data into the field.