RFC 034: Quality assertions and observations

[dannymeijer]

Use this issue to track InQL RFC 034, proposed in PR #60 at docs/rfcs/034_quality_assertions_observations.md.

Area

• Specification (RFCs)
• Documentation

Summary

RFC 034 defines quality assertions and quality observations as structured InQL evidence attached to semantic targets.

Motivation

Data quality checks should be traceable, local, and reviewable. They should not live only in ad hoc test scripts, backend-specific constraints, or external quality products with no connection to the plan lineage.

Proposal sketch

• Define assertion targets over semantic plan fields, relations, and outputs.
• Define predicate and expectation metadata for quality checks.
• Record observation states such as pass, fail, unknown, and skipped.
• Associate observations with execution attempts where applicable.
• Keep quality semantics separate from adapter-specific execution details.

Alternatives considered

• Treat quality checks as ordinary unit tests only.
• Encode quality as backend-specific constraints.
• Defer all quality evidence to an external product.

Impact / compatibility

This is additive. Existing query execution should remain unchanged while future implementations gain structured quality evidence.

Implementation notes (optional)

Review PR #60 for the draft. This work depends on stable semantic targets and metadata attachment contracts.

Checklist

• I checked for an existing RFC or issue covering this.
• I can describe how this impacts existing code and how to migrate (if needed).