Nature of Documents:

The problem of collection, storage and retrieval of documents has been complicated by the following factors:

The steady growth in the output of various types of documents popularly known as the "knowledge explosion" or "information explosion" or "information flood" or "information boom or bloom". 

The publication of documents in various languages of the world. The production of documents in diverse physical forms. 

The nature and complexity of the thought content of the subject matter presented in various forms of documents. 

The complexity of readers' approach to documents and libraries. 

Each document, like an individual, is not only unique but also exhibits relations of considerable complexity with other documents. Extrinsic features like size, colour, volume, binding, year of publication and intrinsic features like thought content and their arrangement inside the document, or the nature of information, i.e., textual, numeric, bibliographic or graphic, also add to the complexity of the problem of libraries for achieving the objective of maximum utilisation of their collections. The complexity of thought content and the nature of relationships between various types of documents must be known and clearly established for their maximum use The maximum use of documents can be ensured by: 

i)  personal assistance to readers, 

ii)  systematic arrangement, and 

iii)  proper display of materials in the library. 

If the collection of a library is arranged in a systematic way documents can be located and retrieved easily. A classification scheme is the map or device for the arrangement of books in the library.