# Mapping Stage — Elaboration

## Criteria Guidance

### Good criteria — concrete and verifiable

- "Every source field maps to a target field with explicit transformation rules (rename, cast, derive, drop)"
- "Incompatible types are listed with chosen resolution strategy and data loss implications"
- "Edge cases document at least: nulls, encoding differences, precision loss, and constraint violations"

### Bad criteria — vague (no clear check)

- "Mapping is done"
- "Schemas are compared"
- "Transformations are defined"

