StatGazerA model review should not create a pile of comments. It should create a structured record of what was found and how each item should influence the decision. That is why taxonomy matters.
Without taxonomy, small documentation gaps can sound as serious as leakage, and unresolved access questions can be mistaken for confirmed defects. The review becomes noisy, and the internal champion has to translate it under pressure. A good taxonomy does that translation before the meeting.
Confirmed defects
A confirmed defect is supported by evidence and changes the interpretation of the model. Examples include future information in a feature, an incorrect target definition, a broken cost calculation, a train/test split that leaks labels, or a production path that does not match the research path.
Confirmed defects should be written with evidence, severity, and decision impact. The memo should state whether the defect invalidates the result, narrows the use case, requires remediation before deployment, or simply changes the confidence level.
Material assumptions
Some items are not defects. They are assumptions the team may be willing to own if they are explicit. Capacity, liquidity, stationarity, benchmark choice, execution model, monitoring cadence, and the treatment of missing data can all be defensible. They become risky when they are invisible.
A material assumption should be stated with the condition under which it holds. That turns the review into a decision tool. The model may be acceptable for research triage but not for allocation. It may be acceptable for a liquid universe but not for a capacity-constrained one. It may be acceptable for a short pilot but not for a recurring oversight process.
Unresolved questions
Unresolved questions are not the same as failures. They mean the review could not verify something because evidence, access, time, or documentation was missing. Treating them as a separate class is honest and useful.
For example, a reviewer may not have raw vendor history, production logs, or the full model lineage. The memo should say what could not be tested, why it matters, and what evidence would close the question. That gives the team a clear path instead of a vague warning.
Limitations and remediation
A limitation is a boundary of use. A remediation item is an action. Mixing them creates confusion. “The model has not been tested in a high-volatility regime” is a limitation. “Add a regime sensitivity check before the next committee review” is a remediation item.
The best remediation list is ranked by model-use risk, not by how easy the cleanup is. Formatting a notebook may be useful. Removing a point-in-time error matters more. Adding monitoring may matter more than a cosmetic refactor if the model is already used in a live process.
What the taxonomy buys you
A taxonomy makes the review file easier to defend. The PM sees which findings change the investment conclusion. The quant lead sees what to fix. The risk or IC audience sees what remains unresolved. The sponsor sees whether the model can move forward, move forward with conditions, or needs more work before it should influence capital.
That is the practical purpose of model validation. It is not to sound skeptical. It is to create a record that survives technical scrutiny and helps the organization make a better decision.