This requires a highly-structured evaluation and policy-selection algorithm for each
failure mode. It incorporates precise and easily understood criteria for deciding which ( if
any) of the proactive tasks is technically feasibly in the present context, and also deciding
how often and by whom the actions should be undertaken. It incorporates criteria for
deciding whether any task is worth doing, a decision that is governed by how well the
algorithm deals with the consequences of the failure. Finally, if a proactive action cannot
be identified that is both technically feasible and worth doing, the algorithm should lead
the user to the most suitable default action for dealing with the failure.