What is schema on read?

1. The definition reads: "Schema on read is the application of a data schema through preparation steps such as transformations, cleaning, and integration at the time the data is read from the database." 2. So the schema is not absent, it is deferred. The structure gets applied at read time rather than at write time. 3. The three preparation steps the definition names are transformations, cleaning and integration. 4. Defining the schema before anything is written is the opposite arrangement, the one used by the relational model the framework describes as the older default for business systems. 5. This connects directly to the framework's point about unstructured data. When records do not share a consistent structure, forcing a schema at write time is expensive so the structure is imposed later, by whoever reads the data for a particular purpose. _Source: NIST SP 1500-1r2 "NIST Big Data Interoperability Framework: Volume 1, Definitions" (Oct 2019), p.7 section 2 "Terms and Definitions"_