1999 MeSH on the Web. NLM Technical Bulletin. Sep-Oct 1998

Restrictions on Use of MeSH Data

There is no charge for downloading any of the MeSH data available from the NLM Web site. However, use of MeSH file data is subject to conditions which are detailed in the Memorandum of Understanding that must be completed before downloading data.

Available MeSH Files
The following formatted versions of the entire 1999 MeSH vocabulary are currently available:

1999 MeSH Trees in ASCII Format (http://www.nlm.nih.gov/mesh/filelist.html): MeSH descriptors with the tree numbers that place the heading in a hierarchical arrangement. Sorted by tree number.

MeSH in MARC Format (http://www.nlm.nih.gov/mesh/filelist.html): MeSH vocabulary in the USMARC authority format include MeSH descriptors, qualifiers (subheadings), and descriptor-qualifier combination records. Supplementary Chemical Records are not included. For best results, please use a graphical interface.

1999 MeSH in ASCII Format (http://www.nlm.nih.gov/mesh/filelist.html): MeSH descriptors, qualifiers (subheadings), and Supplementary Chemical Records (through July 24, 1998), in ASCII format. This is a tagged format, similar to the ELHILL Unit Record format. However, the data are encoded in ASCII, not EBCDIC. This format also includes Supplementary Chemical Records, with those data through July 24. See Figure 1 for a sample ASCII record.

Figure 1 - Sample ASCII MeSH Format Record:


*NEWRECORD
RECTYPE	= D
MH	= Gene Library
PRINT ENTRY	= DNA Library:T028:ACX:EQV:NLM (1998):961031:abcdef
PRINT ENTRY	= Gene Bank:T028:NON:EQV:NLM (1990):890221:abcdef
ENTRY	= Bank, Gene
ENTRY	= Banks, Gene
ENTRY	= DNA Libraries
ENTRY	= Gene Banks
ENTRY	= Gene Libraries
ENTRY	= Libraries, DNA
ENTRY	= Libraries, Gene
ENTRY	= Library, DNA
ENTRY	= Library, Gene
MN	= G05.275.195
MN	= G05.331.599.110.410
FX	= DNA, Recombinant
MH_TH	= NLM (1990)
ST	= T028
AN	= do not confuse with GENOMIC LIBRARY; do not confuse X ref GENE BANK with BIOLOGICAL SPECIMEN BANKS; no qualif
PI	= Base Sequence (78-89)
PI	= Cloning, Molecular (80-89)
PI	= Plasmids (78-85)
MS	= A large collection of cloned DNA fragments from a given organism, tissue, organ, or cell type. It may contain complete genomic sequences (GENOMIC LIBRARY) or complementary DNA sequences, the latter being formed from messenger RNA and lacking intron sequences.
PM	= 90
HN	= 90
MED	= 2295
MED	= *224
M90	= 3520
M90	= *357
M85	= 253
M85	= *33
M80	= 1
CATSH	= CAT LIST
DA	= 890515
RO	= O:PXP
RO	= A:SJN
RO	= M:AGS
MR	= 970620
DC	= 1
DX	= 900101
UI	= D015723

ASCII MeSH contains all data that are present in ELHILL MeSH, including cross-references and scope notes. Online descriptions of the data elements in each file are available for each of the three record types: Descriptor Data Elements, Qualifier (subheadings) Data Elements, and Supplementary Chemical Record Data Elements. Publication Types (PT) are encoded as MeSH Descriptors even though they appear in the PT field and not the MH field in the MEDLINE citations.

Availability of Data

The data for Descriptors and Qualifiers are updated annually and users of the data are encouraged to obtain the new year's data. Supplementary Chemical Records are updated in ELHILL MeSH on a daily basis and the current file in ASCII MeSH is complete through July 24, 1998. The Supplementary Chemical Records will be periodically updated in ASCII MeSH too. The data elements that require a descriptor MeSH heading value, such as the Heading Mapped-To (HM) element, have been updated to match a descriptor in 1999 MeSH.

MeSH Descriptors and Qualifiers are also published annually in print as the Medical Subject Headings, Annotated Alphabetic List. Some Descriptor data are also published in Medical Subject Headings, Tree Structures, and Permuted Medical Subject Headings.

ASCII File Format

Each MeSH record is indicated by a separate line, preceding the record, consisting of the string: *NEWRECORD. (See Figure 1.) Each element or occurrence is contained on a single line. Each line contains an element name and value, for example, MH = Appendicitis. The same is true for longer, free-text fields such the Annotation and Scope Note.

For data elements that are multiply-occurring, each element occurs on a separate line, for example, the MeSH Tree Number:

MN = E05.909.262.607.790

MN = E05.909.262.620.670.620

Generally, data in ASCII MeSH files are in 7-bit ASCII format. The only exception is that in 41 descriptor records, the Annotation element contains one or more diacritical characters. No attempt was made to translate these characters so they may appear differently in different displays.

The file extensions are .bin rather than .txt so that Web browsers will prompt to save rather than automatically trying to display the relatively large text files (up to 36MB). The binary download should have no adverse effects for most users. The lines will usually be transmitted with only a line feed character (decimal 10) and not also a carriage return (decimal 13). Please contact the MeSH Section at the address at the end of this article if you have questions.

Numbers of Records in the 1999 ASCII MeSH File

The number of records in the file for the three record types are shown below.

Record Type Total Records

Descriptors (MeSH headings, including Publication Types) 19,232

Qualifiers (subheadings) 787

Supplementary Chemical Records 101,031*

* through July 24, 1998

Additional MeSH Files Available on the Web

The following MeSH files are also available for download from the MeSH Web site.

1999 Pharmacologic Actions of a given drug (http://www.nlm.nih.gov/mesh/filelist.html)
1999 Drugs with a given Pharmacologic Action (http://www.nlm.nih.gov/mesh/filelist.html)
1999 New Headings with Scope Notes (http://www.nlm.nih.gov/mesh/filelist.html): Main headings that are new for 1999 with scope notes (definitions), cross-references, and other information.
1999 Replaced Headings (http://www.nlm.nih.gov/mesh/filelist.html): Main headings that have changed form for 1999 or have been deleted.
1999 MN (tree number) Changes (http://www.nlm.nih.gov/mesh/filelist.html): Main headings in which there has been a change in the MN (MeSH tree number) for 1999.