ABSTRACT
This chapter introduces a range of principles associated with the concept and use of indexing and searching languages. Displaying search or results sets shows the user how many documents, search terms and references were found, and thereby indicates whether it might be appropriate to further refine the search. Many retrieval systems store sets of search specifications by assigning them a running number. Any system of subject retrieval must then have a mechanism for directing users to other, closely related, subjects. The main means for displaying thesauri is the alphabetic display, but there are also a variety of approaches to systematic display that are useful in displaying relationships. Indexing languages may be of two different types: controlled-indexing languages or assigned-term systems, and natural-indexing languages or derived-term systems. Specificity and exhaustivity are related to the extent that in practice greater exhaustivity needs to be matched by greater specificity in the indexing terms.
