Explains null semantics and three-valued logic
What a null means, and how predicates evaluate to UNKNOWN.
Can AI do this?
AI does this well Most of the tested AI models master this. 10 of 10 models master it.
| Model | Tier | Probability of mastery | Status |
|---|---|---|---|
| gemini-4-argon | Flagship | 100% | Mastered |
| gemini-3.1-pro-preview | Flagship | 100% | Mastered |
| gpt-6-astra | Flagship | 100% | Mastered |
| claude-fable-5-1 | Flagship | 100% | Mastered |
| gemini-3.8-flash | Mid tier | 100% | Mastered |
| gpt-6.1-sol | Mid tier | 100% | Mastered |
| claude-sonnet-5-5 | Mid tier | 100% | Mastered |
| gemini-3.5-flash-lite | Low cost | 100% | Mastered |
| gpt-6-luna | Low cost | 100% | Mastered |
| claude-haiku-5-5 | Low cost | 100% | Mastered |
Mastered means a probability of at least 90% that the model has this knobit, estimated from its graded answers. “Not shown” means the answers do not settle it either way. How the models are tested.
What it looks like in practice
Expected result: What a null means, and how predicates evaluate to UNKNOWN
How it is assessed: Predicts how sample predicates treat nulls
Related knobits
Needed for
- K-629 Recognises a sentinel value standing in for null
- K-630 Recognises a null with a business meaning
- K-714 Recognises nulls left to chance in a check predicate
- K-820 Recognises a default inventing a business fact
All 40 knobits of Design the physical data model.
Source: Data-management practice used by the stage 6 reference and review checklist