Although you may not often think of them this way, the navigation aids provided in a publication (such as the table of contents) represent another form of metadata. Tables of contents, lists of tables and illustrations, guides to major structures and even page numbers themselves all provide information about the publication that allow you to quickly move about it, whether in print or digital form.
One of the clear advantages that electronic documents have over print publications is that they provide a faster, easier and all-around better experience for navigating content. Even diehard print fans have to admit that the print table of contents, and its requisite page-flipping approach to finding where you want to go, hardly measures up to hyperlinked entries that immediately reveal the content. And there’s nothing like a table of contents that is instantly available at the push of a button.
It’s not surprising then that pretty much every electronic format facilitates navigation by the document structure, as shown in Figure 2-1. Microsoft Word has the document map, for example, which allows for accessible navigation of all the heading-styled sections of a Word document. Adobe Reader provides similar functionality for PDFs with text headings through the bookmarks panel, and DAISY digital talking books and EPUB 2 both use the Navigation Control file for XML applications (NCX), as does Amazon’s Mobi format.
