Completing and Refining a Structure Diagram

Completing a partly drawn structure diagram means filling in boxes that should be there but are not yet drawn. You look at a box, ask what jobs the thing it describes is made of, and add any missing part on the level below it, joined to its parent.

Suppose the top box of a school trip system reads Book the school trip, and only its first two subsections are shown: Choose a destination and Collect consent forms. A trip cannot go ahead without transport, so Arrange transport has to be added on the same level as those subsections. Putting it underneath Collect consent forms would say something different and wrong about how the system is built, which is why the level matters as much as the box itself.

Refining a diagram

Refining is improving a diagram that already exists, and there are three ways to do it:

• Break a box that still describes too much into smaller boxes underneath it. Collect consent forms is really several jobs, so it gains Print the letters, Hand out the letters and Chase up missing replies.
• Add a subsection that was missed altogether, such as Send confirmation as another main subsection under the top box.
• Add detail inside a subsection further down, for example placing Email the tickets under Send confirmation, so extra detail is added below the top level too.

A box that already holds one small task needs nothing underneath it, so refining does not mean dragging every branch down to the same depth.