Contract specification v2

Summary

v2 of the Causeway contract specification. Replaces the schema-only v1 with a triple: schema, SLA, policy. Every dataset on the platform declares one.

What changes from v1

• Schema: unchanged shape (columns, types, nullability, constraints) but now versioned, with breaking-change semantics enforced at promote time.
• SLA: freshness, retention, and availability move from free-text wiki entries to first-class contract fields.
• Policy: classification (RAG tier), consent scope, and export rights move off the governance wiki and into the contract.

Why a triple, and not three separate artifacts

Because the three move together. A schema without an SLA is a lie. An SLA without policy lets us serve the data to the wrong consumer. A policy without a schema is an unbounded claim. One artifact, one review, one version.

Breaking changes from v1

Any v1 contract missing an SLA block fails validation in v2. A repo-wide codemod upgrades existing contracts by stubbing freshness: unknown, retention: unknown, availability: unknown and opening a steward task.

Discussion

See the linked PR for the full v1-to-v2 diff.