A data contract is the producer's written promise to a dataset's consumers: schema, meaning, quality rules, service levels, owner and version, kept in the producer's repository and checked by its CI.
The Open Data Contract Standard (ODCS) is the vendor-neutral YAML format for contracts, maintained by the Bitol project under the LF AI & Data Foundation (bitol-io/open-data-contract-standard (https://github.com/bitol-io/open-data-contract-standard 1,161 ), Apache-2.0; v3.2.0, 8 September 2026). A contract holds fundamentals (apiVersion, kind, id, version, status), servers (Iceberg 129 , Kafka 129 , PostgreSQL 1,289 , Snowflake and more), schema objects with typed properties, quality rules (library metrics such as rowCount and invalidValues, or SQL with a threshold), slaProperties, and team and support sections.
Data Contracts wrote BookNest's first ODCS contract (demos/ch07/contract/orders.odcs.yaml) for the order files and checked it with a small script. The stream now gets its own contract, enforced by datacontract-cli (https://github.com/datacontract/datacontract-cli 1,077 ) (MIT, 1.2.2), which lints contracts, tests them against a server, detects breaking changes and exports to dbt 37,942 , SodaCL 659,325 , Avro 129 or JSON Schema.