Provide access to the work by means of an identifier (class number) or identifiers (class numbers) for the disciplinary perspective(s) it takes to its subject matter, such as theology or engineering. [type of data: normalized heading—other entity identifiers (non-literal typed)] Use an existing and widely used classification data value standard such as Library of Congress Classification (LCC) or Dewey Decimal Classification (DDC).
Choose the most co-extensive class number available. If there is no single co-extensive class number available, as in the case of an inter- or multi- disciplinary work, add the number of class numbers necessary to summarize the overall disciplinary or multidisciplinary focus of the work. Do not index the work by adding class numbers for the subject matter covered by a chapter or other portion of the work.
If more than one class number is used for a physical item that is located physically on a shelf using class numbers, indicate which class number is determining the physical location of the item by designating it as the item call number (see rule 6.3).