 The [IS Verification] principle deals with information that in principle could be acquired by an agent. The access to some of this information will be blocked, for example, if the agent is oblivious to the correlation that exists between two kinds of situations. In addition, most correlations are not absolute, they admit exceptions. Thus, for the signalling described in [E1] to be really informational, the extra condition that the radar system is working properly must be met. Conditional versions of the [IS Verification] principle may be used to insist that the carrier situation must meet certain background conditions. The inability of an agent to keep track of changes on these background conditions may lead to errors. So, if the radar is broken, the dot on the screen may end up moving upward while the plane is moving south. Unless the air controller is able to recognise the problem, that is, unless she realises that the background conditions have changed, she may end up giving absurd instructions to the pilot. Now, instructions are tied to actions. For a treatment of actions from the situation-theoretical view, we refer the reader to Israel and Perry (1991). 