Catalogers should be careful not to confuse authorized subdivisions with authorized subject headings.
In the following Orbis index display, Periodicals is valid as a topical subdivision (180), a form subdivision (185), or a subject heading (150):
LTLC MORE ORBIS INDEX SEARCH
BIBLIOGRAPHIC INDEX -- 85 ENTRIES FOUND
1 - 19 DISPLAYED
PERIODICALS
1 *ESTABLISHED HEADING (LC 180 bcb)
2 *ESTABLISHED HEADING (LC 185 bcb)
3 *ESTABLISHED HEADING (LC 150 bcb)
* SEARCH ALSO UNDER
4 ADVERTISING MAGAZINE (LC 550 bcb)
(Click here to see all three authority records for "Periodicals.")
However, in the next Orbis index display, Software is valid only as a form subdivision (185); it cannot be used as a subject heading. As you can see, even some LC catalogers have not applied the authority record correctly!
LTLC MORE ORBIS INDEX SEARCH
BIBLIOGRAPHIC INDEX -- 895 ENTRIES FOUND
1 - 9 DISPLAYED
SOFTWARE
1 *ESTABLISHED HEADING (LC 185 bcb)
*SEARCH ALSO UNDER
2 COMPUTER GAMES (LC 585 bcb)
3 JUVENILE SOFTWARE (LC 585 bcb)
--CONGRESSES
4 .EXPERT SYSTEMS FOR SCIENTIFIC <1992> (LC 650)
5 .INTELLIGENT MATHEMATICAL SOFTWARE <1990> (LC 650)
--DEVELOPMENT
6 .DESIGNING OBJECT ORIENTED SOFTWARE <1990> (LC 650)
--LAW AND LEGISLATION--FRANCE
7 .CONTRATS ET LITIGES EN INFORMATIQUE <1996> (LC 650)
CAUTION: Because the LC project to create subdivision authority records is not yet complete, and because LC began by creating records for form subdivisions, there will not always be a topical authority record that makes it explicit that a form subdivision can also function as a topical subdivision.
For example, Exhibitions can be used as a form subdivision, a topical subdivision, or a subject heading, but at this time there are authority records only for its use as a form subdivision (185) and as a subject heading (150). The topical subdivision authority record (180) will be created eventually:
LTLC MORE ORBIS INDEX SEARCH
BIBLIOGRAPHIC INDEX -- 251 ENTRIES FOUND
1 - 19 DISPLAYED
EXHIBITIONS
1 *ESTABLISHED HEADING (LC 185 bcb)
2 *ESTABLISHED HEADING (LC 150 bcb)
*SEARCH ALSO UNDER
3 AGRICULTURAL EXHIBITIONS (LC 550 bcb)
Remember, always verify usage in the SCM:SH when in doubt!