What is the difference between ISO/IEC 24029-2 and 24029-3?

Part 2 covers formal methods for assessing neural network robustness. Part 3 covers statistical methods. The FDIS introduction says statistical methods are complementary to formal methods and explore varying conditions more widely. Part 2 is published; Part 3 is at final draft.

Which should I use?

Both, for different claims. A formal method can establish a property over a defined input region. A statistical method estimates behaviour over a distribution or a sample. The FDIS introduction frames them as complements, not alternatives.

What changed in the definitions?

Part 2 defines stability at the neural network level, as the extent to which output remains the same when inputs change. The FDIS defines it at the AI system level, as the ability to produce invariant output under specified perturbations. The subject, the effect and the trigger all moved.

What does Part 3 make normative?

ISO/IEC 22989:2022 for terminology, ISO/IEC 23053:2022 for the system framework, and ISO/IEC 24029-2:2023 for formal methods.