Open Data Contract Standard

The Data Contract CLI natively uses the Open Data Contract Standard (ODCS) as its data contract format. ODCS is an open, vendor-neutral standard maintained by the Bitol project under the Linux Foundation’s AI & Data umbrella.

A data contract written in ODCS is a single YAML file that describes a data set’s structure, semantics, quality, ownership, and the servers where the data lives.

A minimal contract

apiVersion: v3.0.2
kind: DataContract
id: urn:datacontract:checkout:orders-latest
name: orders
version: 1.0.0
status: active
description:
  purpose: One record per order. Includes cancelled and deleted orders.
servers:
  - server: production
    type: postgres
    host: localhost
    port: 5432
    database: orders
    schema: public
schema:
  - name: orders
    physicalName: orders
    properties:
      - name: order_id
        logicalType: string
        physicalType: uuid
        primaryKey: true
        required: true
      - name: order_total
        logicalType: integer
        physicalType: integer
        required: true
        quality:
          - type: sql
            description: 95% of order totals are between 10 and 499 EUR
            query: SELECT quantile_cont(order_total, 0.95) FROM orders
            mustBeBetween: [1000, 99900]

:::note The CLI also accepts the older Data Contract Specification format (which uses models/fields instead of ODCS schema/properties), but new contracts should follow ODCS — all examples in this documentation use ODCS. Use datacontract init to start from a current template. :::

Key sections

Section	Purpose
apiVersion / kind	Identifies the document as an ODCS data contract and its version.
id, name, version, status	Identity and lifecycle of the contract.
description	Human-readable purpose, usage, and limitations.
servers	Where the data physically lives — the connection details used by test. One contract can have several servers.
schema	The logical structure: schemas (tables/objects) and their properties (columns/fields), types, constraints, and semantics.
quality	Data quality rules, attached to the schema or to individual properties. See Quality Rules.
slaProperties	Service-level expectations such as freshness, retention, and frequency.
team / roles	Ownership and access information.
customProperties	Extension point for backend-specific settings (for example clickhouseType, trinoType, avroLogicalType).

Logical vs. physical types

ODCS separates the logical type (logicalType, e.g. string, integer, number, boolean, date, timestamp) from the physical type (physicalType, e.g. varchar, uuid, INT64).

• The CLI uses the logical type as the portable, server-independent description.
• When you select a server (via --server or the server type), the CLI maps logical types to that backend’s physical types for exports and tests.
• You can always override the physical type per field, or pin a backend-specific type via customProperties / config (for example clickhouseType, trinoType).

Working with ODCS in the CLI

• Author contracts with datacontract init and the Data Contract Editor.
• Validate the structure against the ODCS JSON Schema with datacontract lint. Pass --json-schema to use a specific schema version.
• Compare two versions of a contract with datacontract changelog.
• Generate a contract from an existing system using the importers.

Learn more

• ODCS specification: bitol-io.github.io/open-data-contract-standard
• Data contracts overview: datacontract.com

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