The classifier must first analyse the subject of the work, then arrange the components, or facets, of the subject into the reverse order of the BC2 schedule, going from the most specific to the most general facet. The classmarks for each facet are then combined by dropping the repeated initial class letter from all but the first. This technique is called retroactive notation. As BC2's citation order is inverted, the facet cited first actually comes last in the schedules.