This tip describes LC segmentation practice prior to 1 September 2005. For information on current practice, please see the revised version of the DDC Appendix: Segmentation.

What is segmentation and how do I apply it when copy cataloging?

Segmentation is an aid that helps logically reduce the length of Dewey numbers provided by central cataloging services such as the Library of Congress Decimal Classification Division. The segmentation provided by LC's DCD division is applied according to two different principles. The mark can represent either the end of an abridged number (as found in the abridged edition of the DDC or Abridged WebDewey), or the beginning of a standard subdivision. Thus, a Dewey number can consist of one, two, or three segments.

If the first segmentation mark shows the end of the abridged number, the second one (if any) shows the beginning of a standard subdivision. And the reverse is true; if the first mark shows the beginning of a standard subdivision, the second one (if any) shows the end of the abridged standard subdivision.

Segmentation is a matter of library policy and addresses two of the commonest options exercised by libraries using the DDC: using the abridged edition, dropping the standard subdivisions, or adopting a combination of both options. If your library uses the abridged edition but not the standard subdivisions given in the abridged edition, you will use only the first segment. The other options require you to check whether the segmentation mark represents the end of the abridged number, the beginning of a standard subdivision, or the end of the abridged standard subdivision.

If your library uses the abridged edition plus abridged standard subdivision:a) stop at the first segmentation mark when it shows the end of the abridged schedule number b) ignore the first segmentation mark when it shows beginning of a standard subdivision, and stop at the second segmentation mark (if there is one) as in that case it will show the end of the abridged standard subdivision.

If your library uses the full edition but not its standard subdivisions:a) stop at the first segmentation mark when it represents the beginning of a standard subdivisionb) ignore the first segmentation mark when it shows the end of the abridged edition number, and stop at the second segmentation mark (if there is one) as in that case it will show the beginning of a standard subdivision.

In each case, the "abridged number" includes any number that can be built using number-building instructions found in the abridged schedules (other than instructions about using standard subdivisions). Copy catalogers must be alert for subdivisions including a zero that are not standard subdivisions. For example, 971.06 represents Canadian history since 1911, not the standard subdivision for organizations interested in general Canadian history (which appears in 971.006).

Last revised: 28 October 2005