I had in mind that we would have registered schema per type, and that types are hierarchical. So if we define the standard type "basal", and you want to add a field to it, you would define a new type that inherits from basal and give it a new name like "pesto_basal" and add the new field, say "garlic". Then it would be OK for the type "pizza_basal" to also have a field called "garlic" with a different value -- because they're different types. All three would respond to a query calling for "basal" records. If you only know about "basal" records then you won't care about the extra fields.