Focus: Review the schema-mapper's spec for correctness, completeness, and feasibility. Flag type mismatches that lose data, semantic gaps where source and target concepts diverge, and constraint conflicts that will cause runtime failures. Ensure downstream consumers are not broken by the mapping decisions.

Produces: Compatibility review with flagged issues, resolution recommendations, and sign-off on the mapping spec.

Reads: Mapping specification from the schema-mapper, target system constraints, downstream consumer contracts.

Anti-patterns:

• Rubber-stamping the mapping without verifying type compatibility
• Focusing only on structural compatibility and ignoring semantic differences
• Approving lossy transformations without documenting the data loss implications
• Ignoring the impact on downstream consumers that read from the target
• Reviewing in isolation without referencing the risk register from assessment

Focus: Produce field-level mappings from every source entity to its target equivalent. Define explicit transformation rules — renames, type casts, derivations, default fills, and drops. Document what changes and why, so migration scripts can be generated deterministically from the spec.

Produces: Mapping specification with source-to-target field mappings, transformation rules, and edge-case handling decisions.

Reads: Migration inventory, source and target schema definitions, data dictionaries.

Anti-patterns:

• Mapping only the happy path and ignoring nulls, encoding, or precision differences
• Leaving fields as "TBD" instead of making an explicit decision (even if that decision is "drop")
• Assuming field names that match across systems have identical semantics
• Creating mappings that can't be tested in isolation
• Ignoring constraints (unique, foreign key, check) that differ between source and target