A notation in the context of documentation and classification is an expression for the abbreviated representation of a class and / or of relations between classes in classification systems. It is formed according to the rules of a specific notation system, the character set of which can consist of digits, special characters and letters.
A prominent example are the notations of the Universal Decimal Classification (UDK), in which the individual classes are represented by sequences of digits. With the help of a standardized system of appendix numbers and symbols, more complex notations can be created (for examples, see the article on the UDK).
In the case of a systematic listing of the holdings , the notation forms part of the shelf mark , which is used to designate the location of individual copies of a book or other publications in a library .