Labelling and Ordering Boxes

A structure diagram is only useful if someone else can follow it, and that depends on how you label and arrange the boxes. Each box holds a short description of the task it represents, and boxes that sit on the same level are placed in a sensible order.

Naming each box

Keep every label to a few words and try to begin it with a verb, so the box says what is done rather than what something is. Calculate delivery cost tells a reader far more than delivery, and Print address label is clearer than a full sentence such as this is where the label gets printed out at the end. Vague single words like data or output could mean almost anything, and sentence-length labels are slow to read, so aim for the middle: short, but specific about the action.

Ordering boxes across a level

Boxes on the same level are laid out from left to right in the order the tasks are carried out. Under a box called Post a parcel, for example, you might read across: Weigh parcel, Print postage, Attach label. Reading across a level therefore tells you the running order of that part of the job, which makes the diagram predictable to follow. Boxes on a level are not joined to each other, though — each one connects only upwards to its parent box, with the left-to-right position carrying the order.

When a box needs nothing below it

A box may have nothing beneath it when its task is already small enough to be carried out in a single go. For a box called Weigh parcel, you could add Place on scale and Note the weight below it, while Print postage could sit with nothing underneath, because printing the postage is a single step — splitting it further would add boxes without adding meaning. So branches of the same diagram can stop at different depths: there is no rule that every branch must reach the same level.