In May 2007, the Cataloging Distribution Service (CDS) began distributing a series of subject authority records that were created solely for the purpose of allowing for machine validation of commonly used subject strings consisting of established headings combined with free-floating subdivisions. (Further details about these records can be found in the CDS announcment at http://www.loc.gov/cds/notices/2007-05-25-Subject_Authority_Validation_Records.pdf)
As of this date [May 22, 2008], over 29,000 of these so-called "validation records" have been distributed, and they are continuing to be distributed at an accelerated pace.
The LC Subject Search screen in Class Web was recently restructured to allow users the option of excluding or including these validation records in their search results. Since most users who search for LC subject headings in Class Web wish to retrieve only standard subject authority records, not these special validation records, the default setting for searches is to exclude validation records. Users who wish to include validation records may override the default setting for a specific search by checking the box for this purpose that appears under "Display Options" on the search screen. Those users who wish to change the default setting to always include validation records in their searches may do so via the account preferences screen which is accessible from the Class Web Main Menu screen. On that screen ("Update Account Information"), a checkbox may be selected to always include validation records in subject heading searches. The checkbox can be found under the caption "LC Subject Heading Validation Records."
Cataloging Policy and Support Office
Library of Congress