Footnotes used to be food for hardy scholars, those who had time and inclination to follow a thought path through cites to multiple books and authors. These literary devices gave readers and editors an opportunity to convey their recorded commentary to future readers. Subsidiary and in small type, footnotes had to fit on a page and frequently functioned as no more than pithy pointers.
Enter the Internet and "Long Live the Footnote"! Called "links," living footnotes offer context, commentary and illumination to the core text. Typically, these living footnotes, denoted by a "hot icon" in the text, will open a door for the reader to a relevant file (text, audio, video, graphic) situated on a computer somewhere else in the Internet world. As the context and readers of a book change and adapt to one another, we will probably begin to see the text of books also evolve in response to these two factors. The idea is that Living Footnotes, like birds let out of a cage, will elevate the text to which they are tethered.