SUBJECT INDEXES AND AUTOMATIC DOCUMENT RETRIEVAL: The Structure of Entries in Chemical Abstracts Subject Indexes Available to Purchase

Index entries from the subject indexes to CA can, in general, be converted to ‘normal’ or title‐like phrases by applying simple tests to the positions of prepositions and conjunctions in the entries. Other, more complex, entries can be transformed after somewhat deeper analysis. These manipulations are a necessary preliminary step to the use of the subject‐index language in retrieval. A scheme is outlined for automatically compiling and editing subject indexes by transforming descriptive phrases with regular structure and vocabulary. These transformations, based on the formal structure of language, are shown to be admirably suited to computer manipulation.