Stage 1: ad hoc
Models are built and run manually by individuals. Reproducibility depends on memory. This is appropriate for exploration but risky for anything relied upon.
Stage 2: repeatable
Code is versioned, environments are specified and training can be rerun. Deployment is still manual.
Stage 3: automated
Pipelines train, test and deploy models with minimal manual steps. Automated validation gates protect production.
Stage 4: monitored
Production data and predictions are monitored for quality and drift, with alerts and runbooks.
Stage 5: governed
Lineage, approvals, documentation and risk classification are built into the platform. Organisations should target the stage appropriate to the risk of their models, not necessarily the highest.