LTI is Very Selective in Its Blocking of Headings
There are thousands of bad or ambiguous LC cross-references that need to be "blocked" prior to linking headings during machine processing. LTI blocks any heading containing five or fewer characters from linking during the initial machine link. Selectively, some of these headings are unblocked [e.g., Asia, Iran, Iraq, etc.] where there is no likelihood of an incorrect link being made to an authority record. If blocked by LTI, these headings appear in the unlinked headings list and, if the library believes the authority record is important to its catalog—for example when it contains a useful cross reference or explanatory note—the authority record can always be downloaded from LC.
Four out of five of the blocks involve corporate/conference heading cross-references (41X). For example, the initials AAS appear as cross-references in 20 LC authority records. Neglecting to block ambiguous headings and cross-references can lead to some odd mis-links.
For instance, we received a bibliographic record with the following heading:
110 2 $aBiblioteca Estadual Celso Kelly.$c(Musican)
The pre-authorized heading probably read:
100 0 $aBeck$c(Musician)
Similar problems result when tables are used to expand parts of headings during a pre-processing procedure, without taking into account the entire heading. For example, we have seen many records in which the geographic subdivision $zMelbourne was changed to $zMelbourne (Vic.) when in fact many of the headings referred to the city in Florida.
Unfortunately, once a heading has been mis-linked, a subsequent vendor will find it almost impossible to identify and fix. Only a chance encounter or the presence of an invalid subfield code will allow it to be corrected.