Over the last few years, the EPUB format has gained widespread popularity in the consumer market. The KB has been approached by a number of publishers that wish to use EPUB for delivering some of their electronic publications. Surprisingly little information is available on the format's suitability for archival preservation, apart from Library of Congress' Sustainability of Digital Formats webpages, which contain entries on EPUB 2 and EPUB 3.
So, the KB's Departments of Collection and Collection Care requested a more detailed investigation of EPUB's preservation credentials. More specifically, answers were needed to the following questions:
What are the main characteristics of EPUB?
What functionality does EPUB provide, and is this sufficient for representing e.g. content with sophisticated layout and typography requirements?
How well is the EPUB supported by software tools that are used in (pre-)ingest workflows?
How suitable is EPUB for archival preservation? What are the main risks?
EPUB for archival preservation
The report EPUB for archival preservation is a first attempt at answering these questions as well as possible. It starts out with a simple example that illustrates the general structure of an EPUB file, followed by a more in-depth discussion of specific aspects of the format. It then covers functionality-related aspects such as layout, appearance and multimedia support, and the main differences between EPUB 2 and EPUB 3.
Support by characterisation tools is important for processing EPUB files in an operational workflow, so a brief review (and some preliminary tests) of relevant identification, validation and feature extraction tools is included as well.
To assess the overall suitability of EPUB for preservation, the format was evaluated against a set of widely used criteria (mainly from The National Archives and Library of Congress). The final chapter wraps up the main conclusions, and suggests a number of recommendations.
Since it appears that not much has een published on EPUB within an archival preservation context so far, we would really appreciate to hear your thoughts on the report. Is anything important missing? Did I overlook any relevant tools? Is there anything in particular that you strongly disagree with? Please use the comment fields below to let us know!
In addition, the final chapter contains two subsections with Community Recommendations and Tool Recommendations. These are all things we can do as a community to simplify the use of EPUB in archival settings. Please consider getting involved if you feel you could make a contribution.
Update: revised version of report (July 2012)
Based on the feedback I received on the original report (i.e. the June 18 edition) I just released a revised edition. The main changes are:
Re-ran tests for Unix File with a more recent (5.11) version of this tool
Included tests of Apache Tika (identification + feature extraction)
Included tests of FlightCrew (validation)
Update: follow-up to the report (May 2013)
A substantial number of EPUB-related developments have happened since this report was published, and as a result some of its findings and conclusions have become outdated. This applies in particular to the observations on EPUB 3, and the support of EPUB by characterisation tools. See this follow-up blog post for a more up to date review of these subjects.
Link to report
Johan van der Knijff
KB / National Library of the Netherlands