“Information retrieval did not begin with the Web. In response to various challenges of providing information access, the field of information retrieval evolved to give principled approaches to searching various forms of content. The field began with scientific publications and library records, but soon spread to other forms of content, particularly those of information professionals, such as journalists, lawyers, and doctors. Much of the scientific research on information retrieval has occurred in these contexts, and much of the continued practice of information retrieval deals with providing access to unstructured information in various corporate and governmental domains, and this work forms much of the foundation of our book.” (Christopher D. Manning, Prabhakar Raghavan, and Hinrich Schütze 2008)