What goes on behind the scenes of PubMed? What happens after a term is entered in the command line and the search is run?
PubMed employs a process called Automatic Term Mapping. This means that your search term is matched against (in the following order):
- MeSH (Medical Subject Headings) Translation Table
- Journals Translation Table
- Phrase List
- Author Index
If a match is found in the MeSH Translation Table, the appropriate MeSH term is searched. The original term is also searched as a Text Word.
For example:
Enter mad cow disease and Pub Med will search for the mapped MeSH heading, Encephalopathy, Bovine Spongiform OR the text words mad cow disease.
To see how PubMed constructs your search, click on Details.
If no match is found in the MeSH Table, the system will look for the term in the Journals Table, followed by the Phrase List and then the Author Index.
If no match is found in any of the tables, and the term consists of more than one word, the words will be searched against the tables separately until the system finds a match. If the terms still do not match then "All Fields" are searched.
For example:
The term pressure point will not be found in the tables but, when the phrase is broken down, Pressure will match as a MeSH heading. The resulting search will include Pressure (MeSH Term) OR'ed with pressure (text word) AND'ed with point (All Fields).
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