Another type of index is the external category index, or a “taxonomy” index. (Taxonomies will be discussed in Chapter 6). An external category index is created based on the selection of words in a category. For example, suppose there is a simple category of words for CAR:
When the external category processing encounters the name of a car in the category, the system writes out a taxonomy record. For example, suppose the system found the word “Honda” in the text. The system recognizes Honda as a car because it is in the taxonomy for CAR. The system then writes out two records: one for Honda (which the system would have written out in any case) ...