Annotations are kind of a weird thing to me, at least from a format perspective. Being able to create them is an integral part of the reading experience for many readers, no doubt, but technically they have nothing to do with the structure of an ebook itself. They’re more like a layer that lives on top of the format.
Seen in that light, it’s hard to argue that EPUB itself has to define an annotation framework. Leave it to the reading system developers to figure out annotations in EPUB or any other format they might support, right?
Of course, therein lies a big problem. Leave it the vendors and you get proprietary implementations that can’t travel with your content across devices and apps. You also can’t distribute annotations separately from the content. That’s effectively the world we live in now; another brick in the wall of the walled gardens.
So, it’s not surprising that the IDPF has been working on a framework for annotations in EPUB, based on the W3C Open Annotation work. It walks an interesting line between presentation and storage, which is what I’m going to look at today.