The ability of the parties to a contract to observe each other's performance of that contract, or to prove their performance to the other party Also, the ability to differentiate between intentional violations of the contract and good faith errors An important objective of smart contract design that often comes into conflict with privity
The ability to observe internally the state of internal nodes in a circuit (SM*)
a subset of controllability, to check to see if the user is getting enough information to control a system