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2005 SEPTEMBER–OCTOBER; 346
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October 20, 2005 [posted]
February 27, 2006 [Editor's note added]

Subject Headings in NLM MARC 21 Products

[Editor's Note: The request for comments on discontinuing distribution of cataloging bibliographic records with artificially reconstructed subject strings can be found at http://www.nlm.nih.gov/pubs/techbull/mj05/mj05_art_rec_sub.html.]

in May of 2005, in an effort to streamline cataloging and simplify training of new catalogers, NLM® made a proposal to discontinue distributing its bibliographic records with artificially reconstructed subject strings. This proposal was sent to the RML, MEDLIB, and MEDCAT discussion lists, as well as to all subscribers of the NLM MARC 21 products.

Response to NLM "Unstringing" Proposal

NLM received over thirty (30) responses to the unstringing proposal, with people arguing passionately on both sides of the issue. A small majority of respondents were in favor of unstringing, but NLM found the arguments against unstringing compelling, particularly for libraries in an environment where there is a mix of records using Library of Congress subject headings (LCSH) and MeSH®. As one user pointed out, keyword searching is not impacted by having strings, but once they are taken apart, those who rely on them have lost them forever.

NLM still has a need to make its cataloging procedures as efficient as possible, with practices that make sense and allow us to easily train new staff members. Therefore we have developed the following plan.

String construction to be simplified beginning with 2006 MeSH implementation

Geographic terms (651 field) and publication types (655 field) in LocatorPlus® will continue to attach as $z and $v respectively to the 650 field(s) in record distribution.

NLM will no longer attach age groups to the main headings. In LocatorPlus, existing $9a subfields will be stripped from those MeSH 650s where they currently exist. Age groups were never treated as subheadings by MeSH or MEDLINE®, so this cataloging anomaly in subject analysis will be eliminated.

All MeSH publication types used in cataloging records will be coded 655, with the currently defined second indicator of 2 (rather than the obsolete use of 7 plus $2 mesh). Use of the 659 field will be discontinued. This was an internal artificial distinction that was made based on whether the MeSH term was a $v prior to 1998 or not. There is no need to maintain that distinction now. All MeSH publication types can act as $v and enhance a subject string. Any 655 that is not a MeSH term (e.g., terms from the Art and Architecture Thesaurus, etc.) will be output in distributed records as 655 rather than 650 $v.

NLM will retain the use of $9n to keep from attaching publication types to subjects inappropriately. Publication types will not be attached to age groups that will now be independent headings, because our analysis shows that the majority of those combinations would be inappropriate or nonsensical.

Languages will continue to be appended to these publication types: Dictionary, Encyclopedias, Phrases, or Terminology. The language(s) continue to be drawn from the 041 $a.

All records that are edited because of these changes will be distributed to licensees of our MARC 21 files. Once these have been loaded by the licensees, there will no longer be NLM records in the utilities with outdated subject practices.

This means that a record which appears in NLM’s LocatorPlus database in the form:
650 _2 $a Main heading $x topical subheading
650 _ 2 $a Age group
651 _2 $a Geographic location $x topical subheading
655 _2 $a Publication Type/Genre
Would be distributed as:
650 _2 $a Main heading $x topical subheading $z Geographic
                    location $v Publication Type/Genre $x language (if applicable)
650 _2 $a Age group $z Geographic location $x language (if applicable)

Actual before and after samples are given at the end of this document.

NLM believes that this compromise approach best meets the needs of all our users. The majority of the subject string is preserved for those libraries and researchers who need it. While libraries that get records both directly from LocatorPlus and a utility may still need to edit records from one of those sources for consistency, the process of stringing/unstringing is clearer and simpler. This simplified practice also ensures more consistency and better quality of records coming from NLM.

NLM plans to make these changes beginning on or about November 21, 2005. Revised records will be distributed as part of the annual redistribution, in December 2005, of all records that have been affected by NLM’s year-end-processing to implement the MeSH 2006 vocabulary. A more specific schedule for the redistribution will be announced to licensees no later than November 21.

Examples:    
 
1.      
Currently in LocatorPlus:
650
12
  $a Geriatrics
650
22
  $a Aged
650
22
  $a Delivery of Health Care $9a
651
2
  $a United States
655
7
  $a Directory $2 mesh
 
 
Current MARC 21 distribution
650
12
 
$a Geriatrics $z United States $v Directory
650
22
 
$a Delivery of Health Care $x Aged $z United States $v Directory
 
 
In LocatorPlus in 2006
650
12
 
$a Aged $9n
650
12
  $a Geriatrics
650
22
  $a Delivery of Health Care
651
2
  $a United States
655
2
 
$a Directory
 
 
2006 MARC 21 distribution
650
12
 
$a Aged $z United States
650
12
  $a Geriatrics $z United States $v Directory
650
22
  $a Delivery of Health Care $z United States $v Directory
 
 
2.
Currently in LocatorPlus:
650
12
  $a Drug Interactions $9a
650
12
  $a Pharmacokinetics $9a
650
22
  $a Breast Feeding $9n
650
22
  $a Pregnancy
655
7
  $a Handbooks $2 mesh
 
 
Current MARC 21 distribution
650
12
 
$a Drug Interactions $x Pregnancy $v Handbooks
650
12
  $a Pharmacokinetics $x Pregnancy $v Handbooks
650
22
  $a Breast Feeding
 
 
In LocatorPlus in 2006
650
12
 
$a Drug Interactions
650
12
  $a Pharmacokinetics
650
12
  $a Pregnancy $9n
650
22
 
$a Breast Feeding $9n
655
2
 
$a Handbooks
 
 
2006 MARC 21 distribution
650
12
 
$a Drug Interactions $v Handbooks
650
12
  $a Pharmacokinetics $v Handbooks
650
12
  $a Pregnancy
650
22
  $a Breast Feeding
 
 
3.      
Currently in LocatorPlus:
650
12
  $a Health Maintenance Organizations $x history
650
22
  $a History, 20th Century
651
2
  $a United States
655
7
  $a Interview $2 mesh
655
7
  $a Personal Narratives $2 mesh
659
7
  $a Oral Histories $2 aat
 
 
Current MARC 21 distribution
650
12
 
$a Health Maintenance Organizations $x history $z United States $v Interview
650
12
  $a Health Maintenance Organizations $x history $z United States $v Personal Narratives
650
22
  $a History, 20th Century $z United States $v Interview
650
22
  $a History, 20th Century $z United States $v Personal Narratives
655
7
 
$a Oral Histories $2 aat
 
 
In LocatorPlus in 2006
650
12
 
$a Health Maintenance Organizations $x history
650
22
  $a History, 20th Century
651
2
  $a United States
655
2
  $a Interview
655
2
  $a Personal Narratives
655
7
 
$a Oral Histories $2 aat
 
 
2006 MARC 21 distribution (no change)
650
12
 
$a Health Maintenance Organizations $x history $z United States $v Interview
650
12
  $a Health Maintenance Organizations $x history $z United States $v Personal Narratives
650
22
  $a History, 20th Century $z United States $v Interview
650
22
  $a History, 20th Century $z United States $v Personal Narratives
655
7
  $a Oral Histories $2 aat


By Diane Boehr
Cataloging Section

Boehr D. Subject Headings in NLM MARC 21 Products. NLM Tech Bull. 2005 Sep-Oct;(346):e6.

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