Mandatory Gate and Preference

In an evaluation, a mandatory gate is a condition that an option must satisfy before it can be considered at all, with a defined pass rule and the evidence that establishes it. A preference is a criterion on which options that have passed the gates are scored and compared. The distinction decides what arithmetic is allowed: preferences can be traded against each other through weights, gates cannot.

Three states, not two

Record each gate as pass, fail, or unverified. A fail excludes the option under the current scope. An unverified gate keeps the option pending until evidence arrives; it is neither a pass by default nor a fail. If every option fails or remains unverified, the conclusion is “no eligible option yet,” not the highest preference total among them. A fictional option that scores 93 on preferences but fails branch isolation stays excluded, and no weight on price changes that.

The UK multi-criteria analysis manual describes the same idea when it defines the zero point of a fixed scale as the lowest acceptable value: any option scoring below it is rejected outright whatever its scores elsewhere. Methods that refuse such trade-offs are called non-compensatory; a weighted sum is compensatory, which is why the gate check has to come first.

Changing a gate is a decision, not a calculation

A gate should carry its source, such as an access policy, a contract, or a required workflow function, and an owner. Relaxing it, for example from per-branch to per-region isolation, requires that owner’s reasoned approval and a review of who is affected. A pass also has a scope: the configuration, paths, and date tested. Evidence for lookup alone does not support a pass for export or cached results.

Not every important criterion is a gate. Calling every convenience mandatory empties the shortlist; leaving a legal obligation as a weighted preference lets a total hide a violation. A release gate before a deployment applies the same logic to a different decision: a candidate version must meet stated requirements before promotion, whatever its other scores.

Reference: UK Government: Multi-criteria analysis manual. Examples here are illustrative.