Completing information flow diagrams

A completion question gives you a partly drawn information flow diagram alongside a description of a system, and asks you to work out what is missing so the diagram matches the description exactly. In a text answer, you name each missing item and say where it belongs. Anything absent or wrong can be the thing you need to supply.

What might be missing

• An entity — a person, department or organisation in the scenario that has not been drawn yet.
• A flow line — a transfer the description mentions but the diagram does not show.
• An arrowhead — a line drawn with no direction, or one pointing towards the sender instead of the receiver.
• An arrow label — a label that has been left off, or one so vague that the reader cannot tell what is being sent.

Compare the description with the diagram

Read the description once and write two lists: every entity it names, and every transfer it describes (who sends what to whom). Then work through the diagram and tick off each entity and each transfer you can find. Whatever is still unticked is what you must supply.

For example, a description of a veterinary practice names the pet owner, the receptionist, the vet and the laboratory. The pet owner passes the pet's symptoms to the receptionist, who sends appointment details to the vet. The vet sends a test request to the laboratory, the laboratory returns the test results, and the vet sends a treatment plan back to the pet owner. If the diagram already shows the symptom and appointment arrows but has an unlabelled arrow from the laboratory to the vet, you supply the label test results. If no arrow leaves the vet for the pet owner, you say that an arrow from the vet to the pet owner is needed, labelled treatment plan.

Check each transfer

For every arrow you identify as missing or incorrect, confirm its tail sits at the sender and its head at the receiver, and that its label names the specific information carried — not just 'information'. Where the description shows information passing both ways, check that an arrow for each direction has been drawn, since each usually carries something different. Finally, remember the diagram should contain nothing the description does not mention, so do not invent extra entities or transfers.