Scientific information is faced with the following problem. On the one hand, we have the world's literature of science and technology, past and present, in many languages; on the other, and enquirer with a question. How to select, from a vast mass of words, the few that are the most closely relevant to an enquiry? It is this selection process that makes use of classification.

p. 3. - Classification and indexing in science (1958) - Chapter 1: The need for classification