Mathematics in Ebooks
Electronic books (ebooks) are used more and more in education, and mathematics
is an important part of this. Design Science is working with the publishing
community, ebook standards organizations, and reading system vendors to ensure
that mathematical notation is handled properly. Besides this page, we have also created an
Ebooks for Math and Science group on LinkedIn, the business networking website. We will use
this group to exchange documents, ideas, and make announcements regarding this
effort. If you are interested in this subject, we encourage you to join.
Equations in EPUB
The EPUB standard is published by IDPF
(International Digital Publishing Forum). While there are other ebook formats,
EPUB appears to be gaining a large following as it is an open, non-proprietary
standard. EPUB is actually several standards in one, each dealing with a
different aspect of the book. For equations, we are only interested in the
content format. EPUB allows two different formats for the content,
DAISY. However, when the ebook world talks
about the EPUB format, they are almost always talking about XHTML, not DAISY.
The latest version of DAISY already has math support anyway as it supports
MathML, so we also will restrict the discussion here to EPUB's XHTML variant.
Specification: Best Practices for Mathematics in
We have created EPUB Math: Best Practices for Mathematics in
Ebooks in order to provide guidance to content providers and reading
system developers on how best to handle mathematical notation in EPUB ebooks. The EPUB standard is complex and most reading systems do not
implement all its features. While reading system vendors may be committed to
implementing the missing features eventually, their implementation priorities
are set according to which features are needed to support specific books and
book collections. This produces a chicken-and-egg situation which we hope to
This best practices document recommends a method for representing
equations in EPUB books involving specific use of EPUB features. This
representation attempts to fit within the following goals and constraints:
- It adheres to the EPUB standard and works within it rather than extend it.
Adding new features and improvements may be an activity we will be involved in
someday but we want to work with the current version of the standard for the
- Equations should be scalable such that they display well on various
devices and zoom levels.
- Each equation must align with the surrounding text (baseline alignment)
and maintain that alignment in the face of font size and zoom level changes.
- We want to enable reading systems to allow equations to be copied to the
OS clipboard to allow users to work with mathematics in other applications.
- Equations should be accessible to people using screen readers with their
ebook reading systems. While DAISY books will give the best reading experience
for people with disabilities, accessibility is important with all ebooks in
- Equations should be available for math-based search.
Our proposed solution involves incorporating MathML to represent mathematical
meaning and structure, vector images in SVG (Scalable Vector Graphics), as well
as fallback raster images (GIF, PNG) for those reading systems that lack SVG
Sample EPUB Books
The following sample EPUB books have been constructed in accordance with our EPUB Math: Best Practices for Mathematics in
Ebooks specification. They can be used to test reading systems, as well as
being helpful to publishers attempting to implement workflows:
Reading System Compliance
Our EPUB Math: Best Practices for Mathematics in
Ebooks contains a requirements checklist for assessing reading systems
compliance. As of this writing, only
Adobe Digital Editions
fulfills those requirements. It is our expectation that this will change soon
as most reading system vendors have pledged to add SVG and embedded font
support soon, as required for full EPUB standard compliance. Whenever any
reading system achieves compliance, we will report it here.
In theory browser-based eReaders, such as
BookGlutton, should be able to render
the MathML in EPUB books when opened on MathML-capable browsers such as Firefox
and Internet Explorer +
MathPlayer. However, in practice they currently do not. The browser-based
eReaders parse ePub files to their standard and, in so doing, filter out
requirements for browser rendering of MathML (for example, some browser-based
eReaders serve ePub files as HTML). Browser adoption of the
HTML5 standard, which includes MathML,
should improve this situation. MathML support, though, is just one step to
compliance of EPUB Math: Best Practices for Mathematics in
We would like to extend the
epubcheck tool to report the number of mathematical equations present in an
EPUB book and check that they follow our best practices specification. As of
this writing, this work has not been started.