RFC 041: Prism plan ingress and external client frontends

[dannymeijer]

Use this issue to track InQL RFC 041, proposed in PR #60 at docs/rfcs/041_prism_plan_ingress_frontends.md.

Area

• Specification (RFCs)
• Documentation

Summary

RFC 041 defines Prism plan ingress for external client frontends such as Spark Connect or SQL-shaped clients.

Motivation

External clients should be able to feed plans into InQL, but they should not make Spark, SQL text, Substrait, or a backend adapter the semantic owner. The correct boundary is an unresolved ingress representation that Prism analyzes into InQL semantics.

Proposal sketch

• Define external frontend ingress into unresolved Prism plan shapes.
• Preserve client session, origin, semantic profile, and coverage context.
• Let Prism perform name resolution, typing, and semantic analysis.
• Keep Substrait IR downstream of InQL semantics rather than as a direct external-client bypass.

Alternatives considered

• Treat Spark as the planner.
• Translate Spark Connect directly to Substrait.
• Model external clients as backend adapters.
• Support only native InQL authoring surfaces.

Impact / compatibility

This is additive and architectural. Future implementations should expand supported frontends without changing the existing authoring path.

Implementation notes (optional)

Review PR #60 for the draft. This work belongs at the external-client-to-Prism boundary.

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).