Form of reference
A referral form or non-preferred term (also Nichtdeskriptor or non-descriptor ) in a documentation language is a name that is not considered descriptor for indexing is used, but instead a synonymous preferred term or different possible descriptors refers.
The corresponding descriptor can be found in a thesaurus under the subentry “UT” (for “used term”) or “BS” (for “used synonym” or “preferred keyword”). The reciprocal relationship is "UF" ("used for") or "BF" ("used for"). This procedure is necessary to maintain the indexing consistency , because if you do not know a permitted descriptor, reference is made to it. The descriptor designates the equivalence class and the non-descriptors the designations contained therein . Non-descriptor lists should be kept as complete as possible in each documentation language , but this can hardly be achieved. The number of non-descriptors is therefore usually higher than the number of permitted descriptors.
example
Thesaurus entry:
Bank
BS Kreditinstitut
BS Seating facility Financial
institution
BS Kreditinstitut
Stool
BS Seating facility Financial
institution
BF Bank
BF Financial institution
Seating
facility BF Bank
BF Stool
BF Chair
Chair
BS Seating