Most libraries request files containing LC authority records that have linked to the library's database during processing. Authority records prepared by LTI are written in accord with the MARC 21 Format for Authority Data.
Separate authority records are extracted for each level of a multi-level heading. For example, three authority records would be extracted from the heading:
English poetry$yOld English, ca. 450-1100$xHistory and criticism.
English poetry
English poetry$yOld English, ca. 450-1100
English poetry$yOld English, ca. 450-1100$xHistory and criticism.
For databases up to 250,000 records, the library can expect to receive about one LC authority record (name or subject) per bibliographic record. The ratio of linked LC authority records to bibliographic records is inversely proportional to database size. For example, in a database of one-half million records the ratio is close to .65-i.e., .65 X 500,000 = 325,000 authority records. Above two million bibliographic records, the ratio stabilizes at about one authority record per two bibliographic records. Linked LC authority records are deduped so that the same record appears only once. LC name authority records are written to a different file than subject authority records. Name authority files contain only LC name authority records. Depending on the library's local system, subject authority files contain both topical and geographic subjects, as well as name authority records for names and uniform titles that have been used as subjects. About 30% of a library's subject authority records are likely to be composed of LC name authority records that have been used as subjects (600/610/611/630 fields).
The default option is for a library to receive all LC authority records referenced in its bibliographic records. Upon request, libraries may instruct LTI to return only those authority records that contain a see (4XX field) or see also (5XX field) reference. About two-thirds of LC authority records contain a cross-reference.
In May 2007 LC announced its intention to begin creating and distributing "Subject Authority Records for Validation Purposes." The reasoning behind the project was to reduce the cost of subject cataloging by providing more subject string authority records for popular and frequently-assigned headings. Presumably, they would also make it easier for local systems to validate LCSH subjects. To date these authority records are limited to: (a) 651 subject heading fields for country names followed by free-floating subdivisions; and, (b) subdivisions found in Free-floating Subdivisions: an Alphabetical Index that appear after topical and geographic headings. They are barebones records containing no references and identifiable by the presence of a 667 field [nonpublic general note] that carries the text "Record generated for validation purposes." While this type of authority record may be useful in an ILS that requires an authority record for every controlled heading or for libraries that lack a comprehensive authority service such as AEX or AUP, some LTI clients have asked that they be excluded from their subject-related authority records. As their number grows and their value is questionable to some, LTI has responded by adding an option to not return subject authority records containing 667 with the validation purposes note.
Similarly, because a number of libraries have reported problems with the display of non-roman 4XX fields within their local systems, a profile option now exists for AEX and AUP users to elect not to receive updated authority records containing 4XX references in non-Latin scripts. LC began distribution of these records in mid-2008 and presently there are over one-half million of them.
Provisional Authority Records
Upon request, LTI will create provisional authority records for unlinked and partially linked headings. After manual review and edit, these records can be upgraded by the library to full authority record status using the local system's authority module. Since most local systems having an authority module can automatically generate authority records for unlinked headings as the records are loaded into the system, few customers have a need for vendor-supplied provisional authority records. LTI's default is not to create provisional authority records.
"Deblinding" Authority Records
LC authority records are structured so see references never point to a heading that is not found in the library's database. In other words, see references are already deblinded and do not require further processing on the part of the authority control vendor.
Deblinding can also refer to the removal of certain see also references. Deblinding at this level prevents the occurrence of see also references when the see also from headings are not present in the catalog. For example, deblinding would prevent the see also reference Baked products see also Bread when there are no records with the heading Baked products but there are records with the heading Bread. LTI recommends that such references be retained since the see also information may be helpful to patrons even when the see also from heading is not currently used in a catalog record.
The following summarizes a posting to the LTI Users List and makes an excellent point. "Blind references" in an online catalog do not result in wild-goose chases in the same way they might have in card catalogs. Take, for example, the reference "Ho, Ho see He, He". In a card catalog the user would have to flip through cards to find out what, if anything, was filed under "He, He." Some references would involve opening new drawers, and depending on the size of the catalog, covering a bit of ground. However, many online catalogs tell one right away what to expect, e.g., Ho, Ho see He, He (0 records). Even if the number of records does not display up-front, the correct form should only be a click away. Informing users what the authoritative heading is, and that there is nothing there, actually prevents wild-goose chases. This is especially true of subject headings, with their sometimes counter-intuitive forms.
LTI Authority Reports
At the conclusion of an authority control job, libraries receive summary statistics showing authority record link rates for name, series, and subject headings. LTI's Final Link Report details the number and percentage of name, series, and subject headings that have linked fully, linked partially, or not linked to either an LC or LTI authority record. Included in the report is a table showing the frequency of each controlled heading field, the number and percentage of headings both validated and not validated against an LC authority record, and the number and percentage of headings changed following the final link procedure.
Every authority control job, be it batch or the ongoing Authority Express (AEX) service, generates an ASCII text file of unlinked headings. These files can be loaded into a word processor for review purposes. In reviewing the unlinked heading reports, one should keep in mind that in the vast majority of cases, the only thing "wrong" with these headings is that no LC or LTI authority record exists for the heading. Most clients do not systematically search unlinked headings in nationally distributed authority files.
880 Field Data
While LTI does not authorize alternate graphic representation data in 880 fields, there are two reports available for batch and continuing authority control services that make it easier for libraries to update 880 field data. These reports are produced at no charge but they must be specifically requested by the library.
The first lists controlled headings with $6 that were changed during authorization. Each change is shown when it happens but not repeated in subsequent processing-i.e., continuing authority control service reports. This ASCII text report may be reviewed by library staff to make needed edits to the corresponding 880 fields. Format of data shown on the changed report includes the bibliographic record control number, the tag and content of the controlled heading field before updating, tag and content of the revised field after updating, and the content of the linked 880 field that may require local revision. Note that the original data is displayed as raw ASCII.
A second report lists errors in 880 fields, such as bad parsing of $6 data or the field linked to the 880 is not present in the catalog record. For AUP users receiving changed bibliographic records this report continues to list errors until they no longer exist in the copy of the database maintained at LTI-i.e., unless the "base file" is replaced, even if the library makes the needed corrections locally. Format of data includes the bibliographic record control number, the tag and content of the controlled heading field with $6, the tag and content of the linked 880 field (again raw ASCII), and a brief explanation of the error found.