Interpreting system diagrams

Interpreting a system diagram means working out what it shows: you identify its components (the parts), its processes (the jobs carried out) and its connections (the lines and arrows between them), then explain how they work together. The labels and the arrangement of the parts help you work out what each element does, even in an unfamiliar organisation.

Finding the parts and processes

Start by listing every component you can find, such as a device, a person or a store of data, and say what each is for. Then do the same for the processes, such as a check or a payment, and for what a person does with a computing resource.

For example, a bike-hire shop's system might include a counter terminal, a hire database, a tracker on each bike, a member of staff and a customer. The processes are recording a hire, taking a payment and updating a bike's location, while staff enter hires on the terminal and customers pay.

Following the connections

Every line and arrow is a link, and an arrow shows which way information or actions pass. Ask yourself what feeds into what, and which parts depend on each other. In the bike-hire example, an arrow from the tracker to the database shows location updates travel that way, so the database depends on the tracker.

Explaining the whole system

Join the parts, processes and connections into a short explanation: the staff member records a hire on the counter terminal, which updates the hire database, and the tracker sends the bike's location to that database, so staff can see where every bike is. That shows what depends on what, and where people interact with computing resources.

The same steps work in any context, including an organisation you have never come across.

Questions about system diagrams are text based, so a diagram is described in words and you will not be asked to draw one. Answer by naming the parts, processes and connections and explaining what they show about how the system works.