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Ebook-technology layers

When you open an ebook on an ereader, what you see is determined by several layers of technology built on top of each other.


  The text you see  
is tagged and formatted in simple computer code (usually HTML and CSS)
stored in a particular file format (e.g. epub, mobi)
possibly encrypted with digital rights management (e.g. ADEPT, Fairplay)
that can be opened by a software application (e.g. Adobe Digital Editions, iBooks)
running on an operating system (e.g. iOS, Android, Windows Phone, Mac OS, Windows 7, Ubuntu, etc.)
installed on a device (e.g. iPhone, Samsung Galaxy Tab, iRiver Story)
with constraints chosen by a manufacturer (e.g. Apple, HTC, Acer, Amazon)


Each layer limits the possibilities for the next layer up. For instance, HTC makes phones, and not e-ink readers. The device is limited by the manufacturer. Or, only certain software applications can run on iOS.

So, as consumers, when we choose a device, we’re inadvertently limiting ourselves to the layers above ‘device’. When we choose to use a particular software application, we’re limiting ourselves to certain DRM, file format, and rendering possibilities. As publishers, we make similar limiting decisions when we choose how to produce our ebooks, or manage our digital catalogues.

Arthur Attwell 20 February 2012
This information is more than two years old, and may no longer be accurate.