Books: Entering the Age of Glosses
Here's the key to thinking about the future of writing, something straight out of the manuscript era: the humble gloss or "scholia," for those who prefer the Latin. They are the notes, in margins, footnotes at the bottom of a page (the standard starting around 1700) and later in the history of books endnotes at the back of the volume or in a separate appendix, that add interpretations, background information, commentary and definitions.