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United States National Library of Medicine National Institutes of Health

Fact Sheet
Online Indexing System

The production of MEDLINE® is streamlined by an online indexing and management system that supports journal control and tracking, input of descriptive bibliographic data, subject analysis of articles, and automatic generation of management statistics on indexing in progress and work completed. Operational since 1984, the system is enhanced continually to reflect new medical terminology and changes in the MEDLINE data base.

The initial portion of the online indexing record for each journal is input in the Serial Records Section (Technical Services Division), at the point of check-in. A machine-readable bar code label is affixed to each Special List journal issue, and read into the check-in record along with the journal volume number, issue, and date of publication. The bar code label is used to call up the record for the journal when it is processed at subsequent points in the production work flow. The system tracks each journal as it moves from step to step, and supplies reports to warn of possible backlogs.

After check-in, journals are transferred to the Index Section (Bibliographic Services Division), and are sent to an NLM contractor for selection, editing, and keyboarding of descriptive data for each article, including author, title, language, abstract, and pagination. Descriptive data are transmitted nightly to NLM for machine validation of key data elements. The journals are then returned to NLM for indexing.

Indexers analyze each article by reviewing the complete text and interacting with a series of formatted screens displayed on their computer monitors. The first screen displays most of the bibliographic data for the article, and the second screen displays the abstract. A program designed to prevent misspellings and typographical errors from appearing in MEDLINE compares textwords in the title and abstract with a dictionary file. Any words not in the dictionary are highlighted for action by the indexer, who must either correct the misspelling or override the warning.

The final two screens allow the indexer to add the appropriate subject headings, qualifiers, check tags, and publication types to the article record. Subject headings, qualifiers, and check tags are selected from NLM's controlled vocabulary, Medical Subject Headings, also known as MeSH® , and are validated against the MeSH file for spelling and authorized main heading/qualifier combinations. The indexing system allows for online interaction with the MeSH file to display the annotation (indexing instructions), scope note (definition), and allowed qualifiers for any specific term. This feature enhances the indexers' ability to select rapidly the most appropriate terms for each journal article. Publication types are also assigned from a predefined list.

Many validations are built into this part of the indexing system. For example, if an indexer adds the check tag "PREGNANCY," the system automatically adds "FEMALE," then displays a message asking the indexer to add "HUMAN" or "ANIMAL." If the indexer adds the MeSH heading "DOG DISEASES" to an article, the program will automatically add the check tags "DOGS" and "ANIMAL." Use of the publication type "PRACTICE GUIDELINE" will prompt the indexer to enter the name of the sponsoring organization at the end of the guideline's title. Various warnings, reminders, and suggestions may be invoked by the program whenever specific headings or qualifiers are assigned. Warnings may be overridden by the indexer, but error messages, concerning misspelled MeSH headings or invalid qualifiers, may not. The system will not allow a record to be added to the data base until all errors are corrected.

Developed with support from NLM's Office of Computer and Communications Systems, the online indexing system was designed to make production within the Index Section more efficient, and further improve the currency and accuracy of MEDLINE.

Questions about the online indexing system may be directed to:

Index Section, BSD
National Library of Medicine
8600 Rockville Pike
Bethesda, Maryland 20894

Phone: (301) 496-6766

For a complete list of NLM Fact Sheets contact:

Office of Public Information
National Library of Medicine
8600 Rockville Pike
Bethesda, Maryland 20894

Fax: (301) 496-4450

Last updated: 24 February 2005
First published: 12 August 1998
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