Once these are recognised, how are they used to enter a document subject into the system? Consider a subject that might occur in the Food technology classification outlined earlier: “the fortification with vitamins of infant foods made from cereal flour”. For a catalogue, a faceted class number might be constructed that would represent the subject as:
Technology-Food technology-Food product-(for) Infant-(from) Cereal-(in the form of) Flour-Fortification-(by)Vitamin.
For Web use, the classifier might well be expected to produce a subject entry for the document by entering each term from “Food product” on, but he would hardly be expected to check Technology and Food technology. If the subject were simply “fortification by vitamins”, he might enter only these two terms, which in this classification figure as subfacets of “Conversion”.