Searching for text documents

Many documents contain, besides text, also images, tables, and so on. This chapter concentrates on the text part only. Traditionally, systems handling text documents are called information storage and retrieval systems. Before the World-Wide Web emerged, such systems were almost exclusively used by professional users, so-called indexers and searchers, e.g., for medical research, in libraries, by governmental organizations and archives. Typically, professional users act as “search intermediaries‿ for end users. They try to fig out in an interactive dialogue with the system and the end user what it is the end user needs, and how this information should be used in a successful search. Professionals know the collection, they know how documents in the collection are represented in the system, and they know how to use Boolean search operators to control the number of retrieved documents.