Conformance checking feels like the end of the job. You run the validator, the report comes back clean or close to it, and the dataset is pronounced ready. We want to make a narrower and more useful point: the check is trivial to write, the running of it is where all the value is, and a passing check on its own is worth almost nothing as evidence. To make the first part concrete, here is a small conformance check in R. To make the second part concrete, here is what it is missing.

A check is just a function that returns findings

A conformance rule is a question asked of a dataset that returns the rows where the answer is no. That is it. Here are three rules that cover a surprising amount of real world trouble: a required variable is missing, a key is not unique, and a date is not valid ISO 8601.…