Classify
Sort until the sorting rule appears.
The Bechers: hundreds of water towers, identically framed.
Seen in Bernd and Hilla Becher, Anonyme Skulpturen, 1970
Try it on your work
Sort every item of one collection (the pile, the drawer, the folder) into categories of your own invention, until nothing is uncategorised. The category you had to invent near the end is the interesting one.
List everything your project must handle and sort the list under headings you write yourself, not inherited ones, until every item sits under exactly one heading. The items that wanted two headings are where the structure will fight you.
Take the classification your project already uses and re-sort the same contents under a different principle: by who touches it instead of what it is, by age instead of type. What moved furthest is what the official scheme was hiding.
How it has been used
Sort the instances until the system appears: the botanist's trays, the hundred photographs grouped and regrouped, the inbox sorted five different ways. The move forces the criterion into the open: every sort commits you to saying what it was sorted by, and "it felt right" voids the sort.
Where it leads
Grouped under Help me name what matters