The contracts on a dataset: for each field, the values it allows and their synonyms, each value's definition with examples that count as it (includes) and that look like it but don't (excludes), what the field is for (description) and where its definitions come from (source), whether it takes one value or many, whether it is a safety field (policy 'ratchet', meaning values can be added but never quietly removed), its confidence threshold and its version. This is the vocabulary the customer asserted; read it before reasoning about any field value.