Chain Indexing
CHAIN INDEXING ➨ Chain Indexing or Chain Procedure is a mechanical method to derive subject index entries or subject headings from the class number of the document. It was developed by Dr. S.R. Ranganathan. He first mentioned this in his book “Theory of Library Catalogue” in 1938.
In Chain Procedure, the indexer or cataloguer is supposed to start from where the classifier has left. No duplication of work is to be done. He/she has to derive subject headings or class index entries from the digit by digit interpretation of the class number of the document in the reverse direction, to provide the alphabetical approach to the subject of the document. Ranganathan designed this new method of deriving verbal subject heading in 1934 to provide the subject approach to documents through the alphabetical part of a classified catalogue. This method was distinctly different from the enumerated subject heading systems like LCSH or SLSH. He discerned that classification and subject indexing were two sides of the same coin. Classifying a document is the translation of its specific subject into an artificial language of ordinal numbers which results in the formation of a class number linking together all the isolate ideas in the form of a chain. This chain of class numbers is retranslated into its verbal equivalent to formulate a subject heading that represents the subject contents of the document. The class number itself is the result of subject analysis of a document into its facet ideas and linked together by a set of indicator digits, particularly when a classification system like Colon Classification is used for the purpose. As this chain is used for deriving subject entries on the basis of a set of rules and procedures, this new system was called ‘Chain Procedure’. This approach inspired in many other models of subject indexing developed afterward, based upon classificatory principles and postulates.
