Definition of an Indexing System 

Let us now look at some of the definitions available in the literature of Library and Information Science. One such definition states that "an indexing system is a set of prescribed procedures for organising the  contents of records of knowledge or documents for the purposes of retrieval and dissemination.", Another definition reads that "an indexing system is the means whereby an indexing language can be applied to make  an index." It appears that both these definitions have common roots. The only difference is that the first definition  is somewhat broader in scope. It may be stated that the need for an indexing system stems out of the work of devising index headings. These index headings mainly relate to documents dealing with compound or multi subjects although, elementary one concept  subjects are  not excluded from the purview of an indexing system. For  convenience, indexing  systems could be divided into two basic  groups: the  pre-coordinate systems and  post-coordinate systems. On the basis of experience, it may be stated that not every index necessarily exhibits all the features of either of these two types of indexing - systems, both types of indexing systems. However, this division is useful in understanding these two categories of indexing systems.