Dogmatic pursuit of “purity” for it’s own sake is rarely beneficial. However the idea behind Ecto’s schemas is that the shape of your data will likely closely mirror the shapes that already exist in your RDBMS’s datamodel - an idea that is rooted in the realm of CRUD applications.
However, as explored in the references in this post, in some “enterprise-y situations” the shape of the data used in the business context(s) may be some strange projection of the data as it actually exists within the RDBMS - at which point DB schema based structures and generic changeset functionality will be much less relevant - so the context defines the shape of the data that it needs to work with (not the repository).
Now if your business context has autonomy over its persisted data (i.e. data is not shared on the level of persistent storage) then there should be fewer reasons for divergent data shapes in persistent storage and the context.
