Subject Indexing Models and Their Principal Features 

A number of subject indexing models have been designed and developed in the past hundred years or so, many of which are in use in libraries and other bibliographical publications all over the world. We can classify them to be of following four kinds: 

1. Authority lists based Subject Indexing Models, e.g., Library of Congress Subject Headings (LCSH), Sears List of Subject Headings (SLSH), etc. 
2. Pre-coordinate Indexing Models, e.g.,Chain procedure, PRECIS, COMPASS, POPSI, etc. 
3. Post-coordinate Indexing Models, e.g., Uniterm Indexing. 
4. Keyword-based Indexing Models, e.g., KWIC, KWAC, KWOC, etc. 

We shall study authority  list-based subject indexing models,  such as LCSH and SLSH, in terms of their back-ground, formation of subject headings in accordance with prescribed principles and postulates, entry format, cross references, filing order, standard vocabulary used, its updating mechanism, merits  and deficiencies. It will be worthwhile to keep the lists handy for reference. This will facilitate your understanding of the lists better.