Portions of this material were previously published as part of the CyberTools MeSH 1999 Update document, mu1999let.doc under the section "V. NLM Cataloging Changes and What We are Doing About Them." Minor changes have been made to make this material more relevant to this context.
Prior to 1999, multifaceted subject descriptors were created by stringing subfields together as:
650 _2 $a Main heading / $x topical subheading / $z geographic / $v publication type/genre [formerly form subheading] / $x language
As of 1999 a number of subfields are split off into separate 650 tags, or into other tags in NLM LocatorPLUS. These are then in many cases reinserted into the 650 tag for distribution to OCLC, etc. These aggregates are called MARCout (after the conversion program) or Distributed Structure (after the purpose). Example of geographic information moved to the 651 tag:
Distributed Structure
650 12 $a Acquired Immunodeficiency Syndrome $x epidemiology
$z Texas
650 22 $a Prisoners $x psychology $z Texas
NLM LOCATORplus Structure
650 12 $a Acquired Immunodeficiency Syndrome $x epidemiology
650 22 $a Prisoners $x psychology
651 _2 $a Texas $x epidemiology
Note that if previously the $z Texas was associated with either the primary or the secondary heading, it will now be associated with both in the external format.
Since NLM recommends that catalogers use the Distributed Structure when cataloging at their own institutions, we will continue to support that structure. Because users of NLM LOCATORplus can save entries that they look up in MARC format and then import them (and there may be other ways), we:
1. Support the older structure;
2. Index relevant tags we have not indexed before to support the
new structure;
3. Provide the MARCout utility that (where possible) can
transform the NLM LOCATORplus structure into the Distributed
Structure.
Specific Issues
1. MARC TAG 650 subfield $z (geographic subdivision)
Examples of this format are given above. In the past we have indexed the $z subfield if it is a MeSH qualifier, and we will continue to do so.
Beginning with this MeSH Update we will now index the 651 tag $a subfield descriptor and the field will be searchable by Keyword. We are also providing a MARCout conversion option that can be applied if:
- there is only one 651 tag, and;
- the 650 tag(s) have no $z subfield, and;
- the value of the 651 $a subfield is equal to the value of
a MeSH qualifier.
The MARCout conversion option will remove the 651 tag and embed an appropriately valued $z subfield in the 650 tag.
The first two conditions above are those that must be true to know how to perform the conversion. The third condition is not much of a barrier to converting the tag (at least for 1999), as almost all of the MeSH geographic descriptors are echoed in geographic qualifiers.
2. MARC TAG 650 subfield $x "in ..." age groups as check tags
Quoting from "Application of MeSH for Medical Catalogers":
Although 1999 MeSH continues to list the "in ... " phrase topical subheadings for age groups, e.g., "in infancy & childhood," etc., NLM catalogers no longer use these to qualify a main heading or main heading and topical subheading combination. In their place, the check tag for a specific age group (i.e., Child, Adult, etc.) or Pregnancy is used to qualify a main heading or main heading/ topical subheading combination.
This first issue is more a problem for MeSH 2000 when these terms are expected to go away. The complete list is:
in adolescence
in adulthood
in infancy & childhood
in middle age
in old age
in pregnancy
The following is a list of age groups that will be used by NLM as topical subheadings:
Infant, Newborn
Infant
Child, Preschool
Child
Adolescence
Adult
Middle Age
Aged
We may provide a conversion utility to assist in converting these terms. The age group terms that are subject headings do not necessarily map one-to-one with the deprecated qualifiers, e.g. there are "Infant" and "Child" -- how do we map "in infancy and childhood"?
NLM is discontinuing the use of these qualifiers, and this necessitates the application of architectural changes this year to support MARC records that NLM distributes. Here are examples of the two NLM formats:
Distributed Structure
650 12 $a Child Development
650 22 $a Communication $x Infant, Newborn
650 22 $a Communication $x Infant
650 22 $a Communication $x Child, Preschool
650 22 $a Communication $x Child
650 22 $a Learning $x Infant, Newborn
650 22 $a Learning $x Infant
650 22 $a Learning $x Child, Preschool
650 22 $a Learning $x Child
650 22 $a Thinking $x Infant, Newborn
650 22 $a Thinking $x Infant
650 22 $a Thinking $x Child, Preschool
650 22 $a Thinking $x Child
NLM LOCATORplus Structure
650 12 $a Child Development
650 22 $a Communication [$9 a]
650 22 $a Learning [$9 a]
650 22 $a Thinking [$9 a]
650 22 $a Infant, Newborn
650 22 $a Infant
650 22 $a Child, Preschool
650 22 $a Child
Note: Subfield $9 a is an internal subfield to be used with the MARCout conversion program to append an age group to a main heading.
The problem for this application is that the age group terms that will be distributed in the $x subfields by NLM are descriptors and this is a position where this application only allows qualifiers. We are adding a list of descriptors that can be used as qualifiers (call it the Qualifying Descriptor Table) that for now just contains the age group terms, Pregnancy, and certain form terms (see below). In the future we may formalize this as a user editable table. This Qualifying Descriptor Table will contain for each term the tag(s) and subfields(s) where the term' s use is appropriate. In other words, a particular term is correctly used in particular tag and subfield combinations. The table will show that the term "Humor", for example, will be allowed in subfield $v of 650 tags and in subfield $a of 655 tags, but not in other contexts.
Armed with this table we are:
a. Able to validate the Distributed Structure above and allow keyword search for an age group in the $x subfield.
b. Providing an option in the MARCout utility to transform the NLM LOCATORplus Structure to the Distributed Structure.
3. MARC tag 650 subfield $v (Form Subdivision) and the 655 tag (form/genre)
Terms of these types are being treated by NLM in several different ways that are discussed below. At present this application is not indexing this subfield or the 655 tag. From now on these will be indexed and searchable by Keyword. Terms that are not NLM PTs (Publication Types) will be totally dropped. NLM LOCATORplus will have no $v subfields.
3.1 PTs used as Form Divisions
The NLM treatment of PTs distinguishes between those considered to be forms and those considered to be genres. The format examples below demonstrate how forms will be presented:
Distributed Structure
650 12 $a Skin Diseases $x diagnosis $v Atlases
650 22 $a Skin Diseases $x therapy $v Atlases
NLM LOCATORplus Structure
650 12 $a Skin Diseases $x diagnosis
650 22 $a Skin Diseases $x therapy
655 _7 $a Atlases $2 mesh
This application will:
a. Add the form division terms to our Qualifying Descriptor Table, to allow both the descriptor version of these terms ($v Atlases) and the qualifier version of these terms: ($v atlases)
b. Index the $a subfield of 655 tags and allow searches by Keyword.
c. Provide an option in the MARCout utility that will convert from NLM LOCATORplus Structure to Distributed Structure (at least where there is exactly one 655 tag).
3.2 PTs used as Genres
These terms will not be distributed in $v subfields, thus:
Distributed Structure
650 12 $a Plants, Medicinal $x chemistry
650 12 $a Quality Control.
655 _7 $a Guideline $2 mesh
NLM LOCATORplus Structure
650 12 $a Plants, Medicinal $x chemistry
650 12 $a Quality Control
659 _7 $a Guideline $2 mesh
This application provides an option in the MARCout utility that
will convert from NLM LOCATORplus format to Distributed Structure.
This application will also index 659 $a tags and make them
searchable by Keyword.