This attribute is used with two different definitions.
- The most common is the name of the thesaurus, ontology, or organization that
established a particular group of keywords, for example,
“MESH”, “ISO-463”,
“IEEE”, “author-generated”,
“ICD9-codes”, etc.
- The second usage describes the type of keyword for some of the more unusual
keyword groups (for example, “hierarchical” for keywords
that are grouped into a hierarchy, “abbreviations” for
keywords that contain an abbreviation and its expansion, or
“code” for keywords that contain a code and its text but
where the source of the codes is unknown).
| Value | Meaning |
|---|
| Text, numbers, or special characters | The source of keywords. This may be an organization (such as
“IEEE”) or the name of a thesaurus, subject index, or
ontology (such as “MESH”). |
| Restriction: This is an optional attribute; there is no default. |