In 1973 F. W. Lancaster published the first textbook about online information retrieval (with E. G. Fayen). That text and his later writings and books on the topics relating to online searching set the precedent for many books to follow. His early work also advocated many changes to the state-of-the-art systems and anticipated many of the characteristics of modern online information retrieval systems. Although the basic underlying structure of modern systems is still similar to what Lancaster wrote about thirty years ago, many of the changes he advocated have occurred. From an era of bibliographic databases on command-driven systems searched by library professionals, online systems have evolved to have friendlier interfaces, inclu...