A diagram of part of a hierarchy of topic names, referenced in examples in the following text.

The hierarchy shown has four levels:

  1. At the top level, the single topic Sport.
  2. At the second level, the three topics Rugby, Football, and Tennis.

    For lower levels, the diagram concentrates on Football while indicating that there are likely to be other subtopics dependent on Rugby and Tennis.

  3. At the third level, there are two topics, Spurs and Arsenal.
  4. At the lowest level, there are three topics.

    The subtopic Results is shown twice, once under both Spurs and Arsenal. The subtopic Signings is shown under Spurs only.