Both indexes and tables of contents include information about where to find things in the book. The WWP considers an index to be an ordered display of some or all of the contents of the book, sorted alphabetically (or in some other way) *by the contents themselves*. We include in the category of indexes any specialized index such as an index of poetic first lines or titles, an index of names or places, a concordance, etc. We define a table of contents as an ordered display of some or all of the contents of the book, sorted *by the sequence in which they appear in the book*.
Note, however, that there is at least one case in the textbase of a hybrid form, which groups the references alphabetically but then within each letter of the alphabet orders them by page number: thus, all the “A” references are together and sorted by page number, followed by all the “B” references and so on.
We will use <div type="index"> to encode things defined by the WWP as indexes (regardless of what the text calls them), and we will use <div type="contents"> to encode things defined by the WWP as tables of contents. Hybrid forms such as described based on their primary mode of organization. Either of these elements may appear at the front or the back of the book; position does not influence our definition of the element.
Note that other kinds of tables and lists, such as subscriber lists, cast lists, etc., do not fall into these categories, since they do not include page numbers or any other way of finding things in the book.
Indexes which are subdivided into sections (e.g. by letters of the alphabet or by category) should be encoded as lists of lists: that is, the index as a whole is a list, and its component items are the groups of entries gathered under each letter or other subheading; each group is also a list. The subheadings themselves are headings to these individual lists. For example (page numbers omitted for clarity):