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The role of standards in digital preservation is widely acknowledged. The current version of the ePub standard, used for publishing and disseminating eBooks, is ePub3, specifically 3.1 (January 2017). A marked difference from ePub2 is support for fixed layout files and, whilst several different ePub readers are available, not all have upgraded to provide full support for ePub3. In late 2017 and early 2018 the British Library’s digital preservation team undertook research into the impact of using an ePub viewer without explicit support for ePub3 on a mixed sample of ePub3 files. The sample comprised 54 files: 20 of these were of fixed layout, the remainder utilized reflowable layouts. For the analysis, content was accessed using two different open source ePub readers: Calibre, which has a wide user base but does not currently explicitly support ePub3, and Readium, which does explicitly support ePub3.
ePub3 files with a reflowable layout broadly rendered to an acceptable standard using both readers. There was one notable exception for both readers, and investigations indicated this was likely due to a problem with the file itself rather than the rendering software. Problems manifested in a more serious way when using Calibre to access just under half of the fixed layout ePub3 files. The rendering of these items inhibited access to intellectual content for example by overlaying it on other content, misrepresenting it, or not including it at all. Other issues that were initially apparent with the other half of the fixed layout sample were mostly resolved by the simple quick fix of switching from ‘page’ view to ‘flow’ view. By contrast, Readium was able to display all of fixed layout files correctly.
The research serves as a reminder that whilst standards remain an essential tool in the digital preservation toolbox, updates to a standard may necessitate changes to the rendering software in use. It further underlines the importance of accurate characterization so that repositories can identify formats at a version level or be able to identify items with explicit rendering needs beyond those served by their default rendering viewers.
This paper was the runner up for the Best Short Paper award.
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