index-type Type of Index

Names the specific indexes in which an index term (<index-term>) should be used, for example, “materials”, “subject”, “chemical”, “regulations and code”.
OPTIONAL on element: <index>
Value Meaning
A word or phrase The name of the index, for example, “species”, “chemical”, “subject”, etc.
Restriction This is an optional attribute; there is no default.
OPTIONAL on element: <index-term>
Value Meaning
One or more words A word naming the index, or a series of words each representing a specific index.
Restriction This is an optional attribute; there is no default.