15.9 Approachability under changing information

In a decentralized problem, the action \(a_z\) may be unavailable to the agent who observes the violated face. An information functor must therefore transport the repair request to an agent with the relevant action, and the returning witness must be visible to the audit observer. Failure can occur because \(S\) is unapproachable, because the information structure blocks the needed response, or because the observer cannot certify the response. UODL keeps these obstructions separate.