We have it backwards.
Use tools like pydantic (Python), Great Expectations (with expect_column_values_to_not_be_null set to fatal ), or dbt 's constraints (enforced, not just documented). If the contract fails, the pipe breaks. Loudly. ab initio data quality
Here is why your data pipeline needs an ab initio mindset shift. Reactive DQ is expensive. You pay the cost of ingesting the data, storing it, processing it, and then again for the engineer who backfills it, and again for the analyst who mistrusts the result. We have it backwards
Change is allowed. Silent change is not. Your first principle is: Schema version is part of the data identifier. events_v2.parquet is a different entity than events_v1.parquet . Never mutate; deprecate. Loudly
Ab initio (Latin for "from the beginning") means starting from first principles. In a quantum simulation, you don't patch errors later—you define the laws of physics upfront. If your initial conditions are wrong, the simulation is worthless.