10.1 Electronic Index - Similarity by Common Keywords

Similarly to the table of contents, the advantage of the index lies in its familiarity to the user. Compared to books, an electronic index offers improved access by allowing the user to jump to an index reference directly by clicking on the entry in the index. Electronic counterparts are also easily constructed automatically based on a list of keywords. An index is one of the simplest means to automatically construct similarity links automatically, because it can be generally assumed that if an index entry points to different pages, theses pages must be somewhat related. In fact, an extension of this simple idea is normally being used to compute similarities and similarity links automatically, based on an automatically generated index, and a computation of similarities based on the information retrieval vector space model (see chapter 1). The linking apprentice discussed in chapter 6.3 uses the same idea to compute links between related nodes automatically. All of the tools presented subsquently in this section use already structured information that is, e.g., stored as semantic networks [Bra79] or as rules.