Computation Layer Metric computation runs on a scheduled basis (hourly, daily, weekly) as defined in the PMM plan. The computation layer must be idempotent and deterministic: running the same computation on the same input data must produce the same result, ensuring metrics are reproducible and auditable. A metric value that cannot be reproduced is useless as compliance evidence. Where metrics depend on ground truth labels that arrive with a delay, the computation pipeline handles late-arriving data and recomputes affected metrics. The recomputation process updates the historical record, and both the estimated and recomputed values are retained (demonstrating the evolution from estimate to confirmed value). The computation layer is typically implemented as scheduled Airflow DAGs, Prefect flows, or similar orchestration tools, with each computation job producing a structured output (JSON or Parquet) that is stored in the monitoring data warehouse and visualised through the dashboard layer. Key outputs

• Scheduled, idempotent, deterministic metric computation
• Late-arriving ground truth handling with recomputation
• Structured output (JSON, Parquet) for audit trail
• Orchestration via Airflow, Prefect, or equivalent