Each step in LTI’s authority control process helps to maximize authority record links and to eliminate incorrect links. Where the full heading in the bibliographic record cannot be validated or linked to an authority record, LTI attempts to link portions of the heading. LTI compares, validates, and updates library headings by computer programs and fix tables. Every batch or backfile authorization project then undergoes some level of editor scrutiny for headings that could not be linked via computer.
In most library databases, we find that with minimal processing about 70% of the normalized headings will match exactly with a 1XX field, or a 4XX pointing to a 1XX, in an LC name or subject authority record. In other words, provided the authority control vendor does not introduce problems that destroy links, with minimal effort any vendor should be able to link seven out of ten library headings to LC authorized access points.
What distinguishes superior authority control is what the authority control vendor does with the remaining 30%.
LTI guarantees 95% or more of a library's controlled headings will be linked to either an LC or an LTI authority record during processing. If that percentage is not achieved initially, we perform whatever additional editor review is needed to raise the library’s overall heading link rate to 95%, at no charge to the client. This applies to all libraries in the United States that adhere to nationally accepted cataloging standards and practices.
How LTI Gets Such a High Link Ratio
LTI compares, validates, and updates library headings by computer programs and fix tables. They use a combination of fuzzy logic and “fix and loop” routines to manipulate and repeatedly test headings against authorized access points. Depending on the type of heading (personal name, preferred title, topical subject, etc.), unlinked headings go through a cycle of routines designed to make high precision full or partial links to authorized access points. Often headings can be validated fully with an authorized access point only after one or more fixes are made to subordinate units.
LTI's fix procedures and tables are based on well-defined rules of what constitutes a valid and invalid heading, as well as on empirical analysis of errors that have appeared in library headings processed by LTI. LC weekly authority record files and current cataloging rules are scrutinized also for changing patterns of usage. Headings that cannot be validated against an LC authority record are checked against 4.8 million LTI-created cross-references from incorrect headings to the authorized LC access point. For example, our files include over one hundred cross-references (chiefly variant forms and misspellings) for Tchaikovsky. Similarly, the subject subdivisions United States and Description and travel are each represented by hundreds of variations (e.g. Untied States, Descripton & travel) in subject subdivision fix tables. If an LC link cannot be made, the heading is matched against a supplemental file of 2.4 million LTI authority records.
Diacritics and special characters are retained in the match key. LTI's normalized headings also retain delimiters and subfield codes. This assists programs that check for links with and without all subfields in the heading. For example, if a personal name heading that contains $c and $d fails to link with an LC authority record, the library's heading is tested for linkage without the subfield $c, and the $d is also checked for permissible variations. For instance, the birth dates $b. 1952, $dborn 1952 and $d1952- are all considered equivalent.
LTI's experienced librarians have devoted years to analyzing why headings do not link, what processing is needed to achieve links, and what changes are needed to bring unlinked headings into conformity with current cataloging standards. We also recognize that every backfile authorization project benefits from some level of editor review. High frequency unlinked headings are always examined. Single-occurrence unlinked headings are reviewed if they fall into one of many categories of software-identified “problem” headings, which include a range of data and content designator errors. Examples are detection of a music subfield code ($m, $r, $o) without the presence of a title subfield, a series that lacks a title, a birth date that falls after a death date, etc.
What About Full Manual Review?
As indicated above, every batch or backfile authorization project undergoes limited editor review for headings that could not be linked via computer. In full manual review, every unauthorized heading that remains after machine processing is reviewed by an editor. Given LTI’s high level of linking with limited editor review, full manual review is not a cost effective approach for most libraries. If during limited review processing 96% of the library's subject headings are validated against authorized headings, there is little to be gained, while incurring substantial additional expense. Prior to providing a cost quote for full manual review authority control, LTI requires that the library submit its entire database for a no-charge evaluation.
For all authority control processing, controlled headings are extracted from bibliographic records and first run through automated processing. Only after a library heading fails to link to an authorized heading does it become a candidate for review by an editor. The critical point is that if a heading is mis-linked during machine processing, that heading will never come to the attention of an editor because it has successfully (albeit incorrectly) linked to an authorized access point. Editors do not check every linked heading in every record to verify that a proper and correct link has been made. Instead, they examine only those headings that failed to link to an authorized heading during machine processing. If editors reviewed every heading linked during machine processing, the authority control vendor’s costs might easily exceed one dollar per record. Few libraries could afford authority control at that price.