There are no uniform classification schemes, yet there are conventions. Levels 1-2 should be represented by alphabetic codes, level 3 and below by numerical ones. Function of a classification scheme is to formalize the order established during arrangement, and relate it to location indexes and fining aids. Often exist within subgroups on a regular repeating pattern, so it may be possible to establish a standard in which they are repeatedly given the same numerical code. The purpose of this is to help users identify relevant material across a number of collections.
Security Often use mnemonic alphabetical symbols.
It is best to assign a permanent reference code at an early stage. This is difficult, though, if the code is to reflect the arrangement of the materials can t do it until the work is done. Ideally, it should be written on each document. A proper workspace is needed, close to conservation unit and storage. The physical process of sorting has priority over any other part of the activity of arrangement.