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NLM Technical Bulletin

NLM Technical Bulletin 1997 Sep-Oct; 298

In This Issue:

dot Year-End Processing (YEP)

YEP of Stored and Saved Searches and Automatic SDI's


Rebuilding of CATLINE®/ AVLINE®

MeSH Coming Attractions

MeSH on the Web

Gold Standard Search

Technical Notes


MEDLINE - 1998 Weekly Update Schedule

AIDSLINE - 1998 Weekly Update Schedule

HealthSTAR - 1998 Weekly Update Schedule

NLM Databases - 1998 Monthly Update Schedule

[This link was removed because it is no longer valid] 1998 NLM Pricing Algorithm Chart

MEDLARS Pricing Schedule

Current Issue


Back Issues


Year-End Processing

New MEDLINE® Backfile and MEDLINE Backfile Configuration - 1998

During 1997 Year-End Processing, all citations published in 1994 or earlier will be pulled from MEDLINE and placed in the appropriate Backfiles. MEDLINE Backfiles and their years of coverage will change again in 1998 with the introduction of a new Backfile called MED93. The primary dates of coverage for MEDLINE and its Backfiles for 1998 will be as shown in the box to the right:

File AliasesCoverage

MED93M93, BACK93, B931993-1994
MED90M90, BACK90, B901990-1992
MED85M85, BACK85, B851985-1989
MED80M80, BACK80, B801980-1984
MED75M75, BACK75, B751975-1979
MED66M66, BACK66, B661966-1974

Reminder to PubMed searchers: PubMed searches MEDLINE, PREMEDLINE® and all Backfiles at one time.

Expansion of Dates in MEDLINE Files for Year 2000

During 1997 Year-End Processing, the following date fields (see Figure 1) in MEDLINE files on ELHILL will be expanded by two-digits to accommodate the new format required for the Year 2000. See Figure 1 below.

Figure 1- List of date fields to be expanded in 1998.

Data Element1997 Search Format1998 Search FormatSearch1998 Display (PRINT)

Year of Publication
97 (YR)1997 (YR)97 (YR)
1997 (YR)
N/A; YR does not display as a separate data element

Entry Month
9712 (EM)199712 (EM)9712 (EM)
199712 (EM)
EM - 199712

Date of Entry
971201 (DA)19971201 (DA)971201 (DA)
19971201 (DA)
DA - 19971201

Last Revision Date
961024 (LR)19961024 (LR)961024 (LR)
19961024 (LR)
LR - 19961024

Class Update Date
97 (CU)1997 (CU)97 (CU)
1997 (CU)
CU - 1997

Date of Publication (DP)

The year of publication is already stored and displayed in YYYY format in the first four characters of the DP, which requires no change for the Year 2000. The DP field must be searched with a four-digit value for the year. For example,

	DP - 1997 Jan 1

is searchable as:

	1997: (DP)    


	1997 Jan: (DP)


	1997 Jan 1 (DP)


Expanded date values must be used when ranging. In MEDLINE files, only the Date of Entry (DA) in the above table of date values is rangeable. For example, in 1998 search:

	FROM 19971201 TO 19971231 (DA)


	GREATER THAN 19971130 (DA)

Unique Identifiers Remain Unchanged

The Unique Identifier (UI) field, a sequential accession number, will not be changing. While the first two digits in this eight number field are date-related, the field value does not represent an actual date. And since the creation of the PREMEDLINE file, there is no longer a strict correspondence between the first two-digits of a Unique Identifier and the year in which the citation is indexed.

Other Databases

Databases containing MEDLINE-derived records (e.g., AIDSLINE®, HealthSTAR® etc.) will reflect the changes described above. Other files and any fields that will have changed displays and search capabilities will be discussed nearer the time those files are class maintained and show the new format.

PubMed and Year 2000 Formats

PubMed contains a searchable Publication Date [DP] field (remember that PubMed search field qualifiers take square brackets) where the year of publication is searchable only as a four digit number, with or without the month and day values. If you choose MEDLINE report for the display format, the year displays as a four digit number in the Date of Publication (DP) field, exactly as it does in the ELHILL version of MEDLINE. For example,

	DP - 1997 Jan 1

is searchable in PubMed as:

	1997/01/01 [dp]


	1997/01 [dp]


	1997 [dp]

Note although the month displays as Jan, you must search for it as a two-digit value.

Ranging on Date of Publication in PubMed may take the following formats:

	1997/09/01:1997/09/30 [dp]


	1997/09:1997/10 [dp]


	1996/12:1997 [dp]


	1996:1997 [dp]

Stay tuned for more information about how non-searchable date-related fields in PubMed will be displayed.

Internet Grateful Med

Searching by date in Internet Grateful Med (IGM) is unaffected by Year 2000 changes. Users will continue to search by selecting the range of years or the individual year from the Apply Limits section of the IGM search screen. Records will display the year in the four-digit format in any applicable date fields.

--prepared by Jan Willis
MEDLARS Management Section
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Last updated: 21 August 2012