Existential viability

There exists an admissible control keeping trajectories in a supplied set K.

Lenses and frameworks

Role. Guarantee. Graph node viable.

For a constraint set K, the viability kernel contains initial states from which at least one admissible continuation remains in K.

— Frames draft §4.6 (Aubin 1990; Aubin, Bayen, and Saint-Pierre 2011)

Viability is content-neutral. It can preserve a correction-supporting region or a captured equilibrium. TSA uses it as the shape of the guarantee, not as a second object: K is supplied by the correction reading.