F4:Compliance Logic
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Summary
F4 Compliance Logic describes how the F4 Application validates GD&T feature control frames against ASME rules and internal constraints.
Scope
F4 validation covers feature control frame structure, datum references, modifier legality, tolerance hierarchy, and feature-of-size requirements. Composite and MSS frames use additional segment rules.
Validation flow
- Parse the feature control frame and extract tolerance type, segments, datums, and modifiers.
- Run automated checks for structure, symbol validity, and modifier legality.
- Ask required user decisions when the standard requires interpretation (pattern application, feature type, true profile location).
- Emit compliance errors or warnings with standardized error codes.
- For composite and MSS frames, validate segment-by-segment once composite rules pass.
Manual decisions
Some checks require user input, such as:
- Pattern application vs single feature.
- Feature type (planar FOS, cylindrical FOS, or other).
- True profile location using basic or toleranced dimensions.
- Datum surface ambiguity for profile controls.
Error and warning reporting
F4 uses standardized error codes and decision IDs to make results traceable. Each validation page lists the rules that trigger errors and how F4 interprets each decision.
Sources of truth
- ASME rule references live in `F4/tests/validators/asme_sections/`.
- Validator implementations live in `F4/app/features/parts/services/validators/`.
- Shared validation utilities live in `F4/crates/validation/`.