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Locking a mechanism map closes an experiment campaign for a defined decision; it does not freeze the material forever. New lots can shift feedstock, processing, humidity history or measurement response. Locked-map monitoring asks whether those lots behave inside the map’s validated envelope. Predictive checks detect important mismatch, and reopening triggers distinguish routine variation from evidence that the mechanism structure or its operational use must be reconsidered.
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Chapter contents
Choose the route closest to the decision, or read from Chapter 1. The chapters remain open; these grouped routes are a navigable index.
Route 1 · Define the decision
Route 2 · Work the ledgers
Route 3 · Transfer the method
Route 4 · Check limits and evidence
Route 5 · Ask and continue
CHAPTER 1 OF 12 · DEFINE THE DECISION
1. Store the lock as a testable contract
The locked record should contain mechanism classes, boundary uncertainty, protocol weights, validated lot range, release action and unlock conditions.
Monitoring tests this contract. It does not compare every new number with an undocumented memory of the original campaign.
CHAPTER 2 OF 12 · DEFINE THE DECISION
2. Choose predictive quantities before new lots arrive
Select quantities connected to the map: class-specific spectra, transition temperatures, recovery curves or boundary-pair similarities. Include both central behaviour and tail or rare-failure features.
A generic goodness-of-fit score can miss the feature that changes the release decision. Use checks aligned with mechanism and consequence.
CHAPTER 3 OF 12 · WORK THE LEDGERS
3. Build a new-lot monitoring ledger
A recycled blend map is monitored over four production lots using preserved reference coupons and current process records.
| Lot | Boundary score | Predictive tail area | Process shift | State |
|---|---|---|---|---|
| L1 | 0.82 | 0.34 | None | In envelope |
| L2 | 0.79 | 0.21 | Small moisture rise | Watch |
| L3 | 0.61 | 0.04 | New supplier fraction | Investigate |
| L4 | 0.58 | 0.01 | Same new supplier | Reopen trigger |
Tail areas are diagnostics, not universal pass-fail probabilities. Thresholds and persistence rules belong to the monitoring contract.
CHAPTER 4 OF 12 · WORK THE LEDGERS
4. Worked reopening rule
The team uses four gates so one noisy protocol cannot reopen the map by itself.
| Gate | Trigger | Observed | Decision |
|---|---|---|---|
| Predictive mismatch | Tail area below 0.025 twice | 0.04 then 0.01 | Not yet by itself |
| Boundary movement | Shift above 0.15 | 0.24 | Trigger |
| Protocol agreement | At least two methods disagree | Spectra and recovery | Trigger |
| Release consequence | Action could change | Yes | Reopen |
Reopening restores multiple maps and the prior safe action until targeted evidence resolves the new condition.
CHAPTER 5 OF 12 · WORK THE LEDGERS
5. Separate alert data from repair data
Use routine lot monitoring to raise an alert, then reserve targeted specimens for diagnosis and later confirmation. Repeatedly tuning and certifying on the same specimens weakens the evidence.
Keep preserved reference material where stability permits. Reference drift can imitate lot drift if instruments or standards change.
CHAPTER 6 OF 12 · TRANSFER THE METHOD
6. Version the map rather than overwrite it
A reopened campaign creates a new version with links to the old map, affected lots, trigger evidence and revised scope. Historical releases remain interpretable.
If the map remains adequate for old feedstock but not the new supplier, branch the scope rather than claiming one universal replacement.
CHAPTER 7 OF 12 · TRANSFER THE METHOD
7. Changed-context transfer: medical tubing lots
Transfer the method to medical tubing where sterilisation and plasticiser variation can alter recovery and cracking pathways.
The transfer check strengthens safety gates, treats traceability by lot as mandatory and retains the approved process whenever monitoring evidence is incomplete.
CHAPTER 8 OF 12 · TRANSFER THE METHOD
8. Connect map locking, influence and uncertainty
Start with the mechanism-map locking guide. Use the consensus-envelope guide to compare new boundary movement.
The protocol-influence guide helps detect an alert caused by one drifting measurement system.
CHAPTER 9 OF 12 · CHECK LIMITS AND EVIDENCE
9. Limits and common misconceptions
Posterior predictive checks can reveal model misfit but do not identify its cause automatically. Lot composition, processing and measurement must be investigated separately.
A statistically unusual lot does not always require a new mechanism class. The question is whether mismatch is reproducible, mechanistically credible and decision-relevant.
CHAPTER 10 OF 12 · CHECK LIMITS AND EVIDENCE
10. Practical evidence checklist
Archive map version, scope, lot genealogy, process conditions, instrument calibration, predictive quantities, thresholds, persistence rules and every alert.
At reopening, preserve affected lots, temporary action, competing explanations, targeted experiment plan, independent confirmation and final version decision.
CHAPTER 11 OF 12 · ASK AND CONTINUE
11. Frequently asked questions
Does every new supplier require reopening?
Not automatically. Treat the supplier change as a monitored covariate and reopen when declared predictive and decision gates are met.
Can one protocol trigger an investigation?
Yes, especially for a high-consequence failure mode, but confirmation should test calibration and independent evidence.
Can a reopened map later return to the old version?
Yes for the old validated domain. Versioning preserves both scopes instead of erasing history.
CHAPTER 12 OF 12 · ASK AND CONTINUE
12. Sources and next reading
Gelman and colleagues’ workflow is summarised in the Stan guide to posterior predictive checks. Strani and colleagues study fused process and NIR monitoring for polymer production. NIST’s measurement-science roadmap describes process monitoring, predictive tools and polymer quality measurement. The lot ledgers are original teaching examples.
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