Relational Indexing

The reading, over the years, of many books and articles about subject indexing has not left me with any impression of well-defined principles, or even clear guidance for the indexing of complex material. I am concerned here with the detailed subject indexing of difficult and varied writings such as are found in a good scientific periodical or, more particuarly, in an abstracts journal in some scientific field. Such indexes require to be very specific and accurate, and as complete in reference to detail as one can achieve, finances permitting. You have only to consider the great value to science of such indexes as that provided for Chemical Abstracts to appreciate the importance of this matter. Nevertheless, I have never seen any exposition of any scheme providing a complete logical approach to such indexing; advice in choice of heading and avoidance of synonyms, suggestions on grouping headings and subheadings, and so on, are available in plenty, but they provide no reliable order of work.