C for Choosing Controlled Vocabulary or Choosing Databases
What is Controlled Vocabulary?
Some databases, like PubMed, use controlled vocabulary subject headings. See if subject headings exist for the concepts represented in your topic. Look at how they are indexed and what kinds of articles you find when you search with them. Collect your controlled vocabulary terms in your document.
Controlled vocabularies are a set of predetermined terms that describe specific concepts. You will find that many databases use their own controlled vocabularies (sometimes called index terms, subject headings, or a thesaurus) to enhance the findability of citations. If you have heard of MeSH, this stands for Medical Subject Headings, and is the controlled vocabulary used in PubMed.
Databases that use controlled vocabularies employ subject specialists who review individual citations and add the appropriate controlled vocabulary terms to the citation that describe all of the concepts covered in the article. Using controlled vocabulary terms in your search strategy allows you to locate citations no matter what term(s) an author does or does not use, and helps account for spelling variations and acronyms.
Controlled Vocabulary: MeSH or Medical Subject Headings
- MeSH stands for Medical Subject Headings. It is a controlled vocabulary of terms assigned to records to make them discoverable.
- These are a standardized set of terms that are used to bring consistency to the searching process. In total, there are approximately 29,000 MeSH terms, and they are updated annually to reflect changes in terminology.
- Use the MeSH database to identify Medical Subject Headings (MeSH) which will help you to find literature indexed with the MeSH term.
- Using MeSH terms helps account for variations in language, acronyms, and British vs. American English.
- MeSH can be searched from the MeSH Database.
- Terms are arranged hierarchically by subject categories with more specific terms arranged beneath broader terms. MeSH terms in PubMed automatically include the more specific MeSH terms in a search. This is called “explode.”
- To turn off this automatic explode feature, click on the button next to, “Do not include MeSH terms found below this term in the MeSH hierarchy” in the MeSH record or type [mesh:noexp] next to the search term, e.g.neoplasms [mesh:noexp]. See next page for additional information on no explode.
- Use the PubMed Search Builder on the right side of the screen to add your selected MeSH term to the box, and click Search.
Explode, No Explode, and Major Heading
- Explode will search with all narrower headings beneath the main heading you have chosen. PubMed will default to explode any MeSH term you search.
- No Explode will only search for your chosen MeSH term without including any of the narrower headings in the MeSH hierarchy. You can select this option from the MeSH record.
- Major Heading will narrow your search to only find MeSH terms listed as a major topic of an article. You can select this option from the MeSH record. Major headings are shown in the article record with an asterisk.
Depending on your experience level, perhaps choosing databases to search is more appropriate than choosing controlled vocabulary. Much will depend on what you have access to. Here are just a few suggestions.
- Web of Science
- Academic Search Ultimate
- APA PsycINFO
- PTSD Pubs
- Social Theory
- Abstracts in Social Gerontology
- Education Research Complete