  This study is centred on the generation of instructions for household
appliances. We show how knowledge about a device, together with knowledge about
the environment, can be used for reasoning about instructions. The information
communicated by the instructions can be planned from a version of the knowledge
of the artifact and environment. We present the latter, which we call the {\it
planning knowledge}, in the form of axioms in the {\it situation calculus}.
This planning knowledge formally characterizes the behaviour of the artifact,
and it is used to produce a basic plan of actions that the device and user take
to accomplish a given goal. We explain how both procedural and warning
instructions can be generated from this basic plan.
  In order to partially justify that instruction generation can be automated
from a formal device design specification, we assume that the planning
knowledge is {\it derivable\/} from the device and world knowledge.
