Read the scenario (Pickerings Properties).
(a) List the functions of the system, as perceived by an external user.
(b) List the external entities. Note that because we are modelling the data flows, not use cases, the external entities should be the actual sources and sinks of data rather than the persons keying in the data.
(c) Produce a context (or level 0) data flow diagram using the method described in the unit materials.