RFC 037: Plan diff and blast-radius inputs

[dannymeijer]

Use this issue to track InQL RFC 037, proposed in PR #60 at docs/rfcs/037_plan_diff_blast_radius_inputs.md.

Area

• Specification (RFCs)
• Documentation

Summary

RFC 037 defines plan diff and blast-radius input evidence for comparing InQL plans and understanding downstream impact.

Motivation

Authors need to understand what changed between plan versions and what those changes may affect. Plain text diffs are not enough for semantic lineage, governed attributes, adapter requirements, or quality evidence.

Proposal sketch

• Compare semantic targets, fields, lineage, requirements, metadata, and evidence links.
• Emit structured diff states for added, removed, changed, and unchanged targets.
• Provide inputs for blast-radius analysis without claiming to own every external dependency graph.
• Preserve enough context for CI and review workflows to explain changes.

Alternatives considered

• Rely only on source text diffs.
• Compare backend physical plans.
• Delegate all blast-radius work to external catalogs.

Impact / compatibility

This is additive. Existing plans remain valid, while future tooling can use structured diffs for safer reviews and governance workflows.

Implementation notes (optional)

Review PR #60 for the draft. This work builds on stable semantic identity, lineage, metadata, and plan bundle evidence.

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).