To facilitate navigation of the content, publications should include a guide to all the illustrations they contain. Without these quick links, there is often no easy way for users to locate the illustrations again. They instead have to navigate through the content of the book until they reach the location.
The EPUB navigation document can be used to provide this functionality. A list of illustrations can be
defined in the same manner as the table of contents, but using a
element with an
epub:type attribute with the value
loi (see Example 1). The
loi nav should contain only a single ordered
list of entries, with each entry linking to a figure or illustrations.
Note that although this type of navigation aid is not formally defined in the EPUB specification,
navigation documents were made extensible for this purpose. When creating an
loi nav, you
should also embed the navigation document as content within the publication as Reading systems may not
provide specialized access to it.
No, using the navigation document simplifies the creation process (i.e., requires creating only one instance for two uses), but is not required for accessibility or other purposes.