A Classification Index is an ordered list (alphabetical, in code order etc) of Classification Index Entries. A Classification Index can relate to one particular or to several Statistical Classifications.
A Classification Index shows the relationship between text found in statistical data sources (responses to survey questionnaires, administrative records) and one or more Statistical Classifications. A Classification Index may be used to assign the codes for Classification Items to observations in statistical collections.
A Statistical Classification is a subtype of Node Set. The relationship between Statistical Classification and Classification Index can also be extended to include the other Node Set types - Code List and Category Set.