The Index is an optional element of a standard, and its inclusion should be considered only for very long and complicated documents, where the table of contents is not adequate to aid the reader in locating a subject. The authors should be aware that any revision to the text may necessitate corresponding revisions to Index entries and that they are responsible for keeping the Index up to date. This will change once a product has been converted to XML and its associated index has been set up to be auto-generated.
An index should enable a reader to find every pertinent statement made in a book; it usually includes both proper names and subject entries. An index, as presented in the Sample, is composed of the following:
The entry, set flush left, is the principal subdivision of an index. A simple entry consists of a heading and what is technically called a locator.
The heading identifies the subject of the entry; the locator tells the reader where to find material pertaining to the subject.
The locator can be a designator, section number, chapter and paragraph number, or any of several other types of place identification. Page numbers should not be used as locators.
An entry consisting of a heading is always broken into subentries. These consist of subheadings, each representing some aspect of the main heading, and locators telling the reader where to find the material.
All indexes are set in what is called flush-and-hang style. This means that the first line of an entry is set flush left and the rest of the entry is indented below it. The first letter of each main entry is set uppercase and the rest all lowercase (unless the entry is a proper noun). If the main entry runs over, it should be indented two ems. The main heading should be separated from the locator(s) by a comma. Each subentry (set lowercase) begins a new line and is indented one em; subentry runovers are indented two ems from the start of the subentry.
Cross-references guide the reader to related information. Properly used, they are extremely helpful adjuncts to an index, but they should never be employed unless they actually lead to additional information, not just the same information indexed under other headings. Cross-references are of two general kinds: "see" references and "see also" references. The words “see” and “see also” should be set in italic. See The Chicago Manual of Style (17.11 through 17.19) for proper usage and examples of cross-referencing.
Index entries and subentries are alphabetized according to the rules listed in C-2.3.
