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  May 8, 2000 [posted]
June 30, 2000 [sentence clarified; Editor's Note added; header clarified; sentence clarified; sentence added]
 Organization of National Library of Medicine Bibliographic Databases

A s part of the National Library of Medicine's (NLM) project to modernize its computer systems, the Library has been reorganizing its bibliographic data into three groups:

  1. Citations to journal and journal-like (e.g., newsletter) articles published mostly from 1966 forward,
  2. Citations to monographs (including book chapters) and to whole serials, and
  3. Citations to selected, individual meeting abstracts, and journal article citations that predate 1966 as a year of publication [clarified, June 30, 2000].

[Editor's Note, June 30, 2000: The year 1966 as used to distinguish between MEDLINE and OLDMEDLINE refers to the indexing year 1966, not the year of publication of the article. This means that about 100,000 citations to articles published in 1965 actually appear in MEDLINE, not OLDMEDLINE, because of the time lag in receipt of the journals after their actual publication as well as the time needed to index. A smattering of citations to even earlier publication years in the 1960's (about 9,000) also exist in MEDLINE. Users should consider searching both files if they are interested in the 1963-1965 year of publication range.]

Journal Citations

Journal and journal-like citations from 1966 forward will reside in PubMed, the NLM's Web-based retrieval system. PubMed contains:

  2. MEDLINE in-process citations, and
  3. Publisher-supplied citations.

MEDLINE citations, the bulk of PubMed at about 11 million citations, are enhanced with MeSH indexing and other value-added data such as publication types; grant numbers; comments, errata, and retractions; and related-accession numbers to genetic databanks. MEDLINE in-process citations (also known as PREMEDLINE) are preliminary (not yet quality controlled) citations, most of which will become indexed MEDLINE citations. Publisher-supplied citations are sent to NLM electronically directly by a publisher. While these citations often contain abstracts, they are not indexed with MeSH and the other value-added data entered, nor do they undergo the strict quality control procedures used by NLM for MEDLINE data. Also, the scope of both MEDLINE and PubMed is expanding to include more life sciences after concentrating in the past on biomedical topics.


Citations to monographs and whole serials will reside in LocatorPlus, the NLM's Web-based online public access catalog. The contents are largely NLM's own physical collection which also includes audiovisuals and historical materials, but some materials cited in LocatorPlus are owned by other institutions, not by NLM. These other institutions are either regional libraries that are part of the National Network of Libraries of Medicine, or are organizations that have cooperative agreements with NLM to create records in certain subject areas such as health services research, space life sciences, bioethics, or family planning/population research.

Meeting Abstracts and OLDMEDLINE [clarified June 30, 2000]

Citations to selected, individual meeting abstracts as well as the journal citations older than 1966 (also known as OLDMEDLINE) will reside in another Web-based collection that is currently under development [clarified June 30, 2000]. NLM is segregating meeting abstracts to speed up their availability. NLM hopes users will also recognize that there are no full-text articles associated with these abstracts.

OLDMEDLINE data differ significantly in structure from more modern MEDLINE data - while the citations contain controlled subject vocabulary terms, those terms have not been validated against the current MeSH vocabulary. This condition would affect retrieval integrity if the OLDMEDLINE data were part of PubMed. (Remember that MEDLINE contains about 109,000 citations to articles published during 1963-1965, as explained above.[added June 30, 2000])

NLM Gateway

This new organization groups data similar in structure or function which has the benefit of optimizing retrieval techniques, as well as streamlining data creation and maintenance behind the scenes. Users who want to concentrate on a particular data publication type can go directly to the appropriate retrieval system, e.g., those who know they want only recent journal literature references will go directly to PubMed. Users who want to search for all bibliographic information on a particular subject may try the NLM Gateway, a new Web-based system expected in Spring/Summer 2000.

The NLM Gateway will be an intelligent search tool that will automatically search multiple systems at the National Library of Medicine and present the results. It will interface initially with PubMed, LocatorPlus, meeting abstracts, OLDMEDLINE, and MEDLINEplus (NLM's Web-based consumer health information service). Future development of the Gateway will provide access to other information systems at NLM such as TOXNET and, while improving the functionality of the evolving Gateway.

Conversion Road Map

For those loyal users of NLM from our mainframe-based days who were used to searching several subject-oriented ELHILL databases, NLM is converting the unique data from those databases into the appropriate group in the new organization. Unique journal citations from HealthSTAR are already in PubMed's MEDLINE and those from AIDSLINE, HISTLINE, SPACELINE, BIOETHICSLINE, and POPLINE will follow. These unique journal citations are becoming part of the enhanced MEDLINE in PubMed. Existing citations will retain their MeSH headings and new citations will continue to be indexed with MeSH. PubMed subject search filters or hedges are expected for most of these topics. Health Services Research will probably develop multiple filters because of the nature of its scope.

Unique monographic citations from HealthSTAR, HISTLINE, SPACELINE, and BIOETHICS are already in LocatorPlus with POPLINE to follow. These citations are tagged in LocatorPlus as contributed by the specific data producer. About 22,000 monographic chapter citations dating from 1976-81 will also be moved from MEDLINE to LocatorPlus.

Meeting abstracts from AIDSLINE as well as the OLDMEDLINE data will be available in the first phase of the NLM Gateway while meeting abstracts from HealthSTAR are expected in a subsequent version of the Gateway.

In the future, citations in both PubMed and LocatorPlus will be shared among NLM and cooperating producers. Rather than having multiple copies of a citation that are each enhanced in different ways by different producers, now there will be only one copy of a citation which may be enhanced in certain ways by these cooperating producers. One enhancement example is the addition of Space Flight/Mission Numbers to citations reporting research conducted in space. Only a small number of unique, non-Index Medicus citations are affected by this shared work flow, yet everyone benefits by not repeating MEDLINE-derived and LocatorPlus-derived citations in multiple places. NLM currently has agreements with the following outside collaborators: the Kennedy Institute of Ethics, the Population Information Program, National Aeronautics and Space Administration, the International Nursing Index as well as contractors working for the National Information Center for Health Services Research (NICHSR), NLM, and NLM's own History of Medicine Division staff.


NLM plans to continue access to Internet Grateful Med (IGM) until the unique data from the old subject-oriented databases are converted into their new homes (tentatively expected by the end of calendar year 2000). Ultimately, having the unique data from these databases become an integrated part of PubMed and LocatorPlus should increase the retrieval of that data by significantly more users, and the NLM Gateway will continue to evolve as a tool for gathering information together from diverse NLM resources using only one search request. This is a time of great change at NLM with the end goal being improved services for the many and varied users of NLM resources.

By Lou Knecht
Bibliographic Services Division black line separating article from citation information

Knecht L. Organization of National Library of Medicine Bibliographic Databases. NLM Tech Bull. 2000 May-Jun;(314):e1.


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