Interpreting information flow diagrams

Interpreting an information flow diagram means turning the picture back into sentences: who sends what, and to whom. Work through the diagram in three steps, and nothing in it gets missed.

Working through it in three steps

1. Identify each entity. List every person, department or organisation shown. A diagram of a gym might contain three: the member, the reception desk and the fitness instructor.
2. Follow each arrow. Note the entity at the tail, which is the sender, and the entity at the head, which receives it. Direction carries meaning: an arrow from the reception desk to the instructor says something different from one pointing the other way.
3. Read each label. The label names the specific information carried, such as 'membership renewal request' rather than the vague 'details'.

Writing it out in words

Put the three steps together and each arrow becomes a sentence of the form 'the sender sends the information to the receiver'. For the gym diagram: the member sends a membership renewal request to the reception desk; the reception desk sends the updated class booking list to the fitness instructor; the instructor sends the weekly training plan back to the member. Naming the sender and receiver of every arrow is what makes the description precise — writing that information 'passes to the next stage' does not say who sent what.

Describe only what is there. If you add a processing step or a store of data, you have started describing something else, because those belong to a data flow diagram.

When the organisation is unfamiliar

A diagram may show an organisation you have never met, such as a ticket office or a research laboratory. You do not need to know how it works: the entity names and the pattern of labelled arrows tell you how that part of it communicates, and that is enough to describe every flow confidently.