F4:Validation Decisions
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Summary
Some GD&T compliance checks require interpretation. When F4 cannot determine an answer unambiguously from model data, it asks a structured question (“decision”) and validates based on the selected option.
Standard meaning
ASME Y14.5 defines the rules, but it does not define how software should collect clarifications when information is missing or ambiguous.
F4 behavior
When F4 asks a decision
F4 emits decisions when a rule depends on context that may not be available from imported CAD/PMI or the current part model. Common examples:
- Feature type classification (planar feature of size vs cylindrical feature of size vs other).
- Pattern application vs single feature.
- Whether basic dimensions exist/are used to locate a tolerance zone.
Decision types
Decision types are tolerance-specific (e.g., flatness feature type, position basic dimensions) plus a few common fallbacks.