Before revision: Schemaless upgrade and downgrade schema upgrade when structures are extended or modified is done by adding or removing Items in new ways at runtime, and there are no upgrade scripts - hence the data model is NoSQL and schemaless.
After revision: Schemaless upgrade schema upgrade when structures are extended or modified is done by adding or removing Items in new ways at runtime, and there are no upgrade scripts - hence the data model is NoSQL and schemaless.