I have an example for a DFD for a patient information system implemented in a certain hospital. The below figure, represents the overview diagram (level 0-diagram, if we consider that the first level is the context diagram then the second level is level 0 diagram and so on):
In this system, patients can search and make appointments. I try to understand the data flow that is labeled patient name
and that is directed from the process Make appointment
to the database Patients
(see yellow hightligh in the diagram).
I don't understand why we have this flow in our system: In which scenario would the process Make appointment
send to the database patients
the patient name ? Shouldn't the patient name already be sent by the process maintain patient info?
Best Answer
You seem to be mislead by the name of the process
Maintain patient info
, which suggests that patient records are created there.If we forget about the assumption and look at the flows involving the
Patients
data store, we can see:Patient Info
flows out toMake Appointement
andPrepare Reports
Patient Info
flows in fromMaintain Patient Info
. But the flow is in labeledUpdate to ...
. This is more restrictive than just an inflow of patient data: it supposes that the data already exists.Patient name
flows in fromMake appointment
.Using DFD semantics and assuming the DFD was drawn respecting the rules, we can understand that:
patient name
is a part ofpatient info
(since it is never extracted explicitly).Remarks:
Perform billing
does not needpatient info
.