Deterministic analysis produces the same output for the same input every time, using explicit rules or arithmetic rather than a learned model.
After an incident, someone will ask why the system did what it did. Deterministic logic can answer by pointing at a number and a constant. A learned model can offer a probability and a shrug, which is the wrong answer at the worst possible moment.
Thresholds, regression, standard deviations and vector distances are all deterministic. They are auditable, reproducible, and cheap enough to run on every reading.
Re-running last Tuesday's readings through the same threshold logic produces exactly last Tuesday's alarms.
The deterministic layer is authoritative. Thresholds, classification, trend and baseline analysis and signature matching all sit inside it.
