Amenda Gomm and Tom McClusky of Digital Bindery presented the results of their testing of Epub 3 elements on various reading platforms. Some elements worked and some didn’t. For metadata, Epub 3 offers a lot: container, publication, structure, and content. Focusing on the publication metadata, there are many optional elements, but when they put these elements into a document they are not supported by the reading systems. The optional areas in the creator and title metadata also didn’t work with a lot of display systems and is should be considered unreliable. Cannonical fragment identifiers are a new Epub 3 feature, but they don’t work at all. There are a lot of navigation features, such as table of contents, page list, and non-linear content that are supported in Epub 3. The basic functionality of table of contents is universally supported, but the Nook won’t nest a table of contents and the Kobo Arc only goes 3 levels deep in nesting, so you don’t know what will happen if you use them. Since good navigation is critical producers shouldn’t nest tables of contents now, or if it is critical there are some more complicated workarounds.
Non-linear content is stuff such as footnotes, ancillary content, and covers, but readers are different as to whether they will support the tags for it. You will need to test your non-linear content on individual readers. Pagelists are the way to tie together the print and ebook page numbers so they are both the same. Unfortunately, support in the readers is minimal. They found the same problems with a lot of the semantics tags, such as for bi-directional reading, as these are not supported by many of the readers that are out there. Interestingly, hyphenation is a nightmare as many readers don’t support it or will display hyphens in strange ways no matter how you try to program them. Page breaks are another problem with inconsistent support. For example, the Kobo Arc will support page breaks in portrait mode but not in landscape mode.
The takeaway from this session is that there are two parts to the ePub equation. The first is that it is important to have standards and ePub 3 is the current one. However, every reading device is different and not many will currently pay attention to the new ePub 3 calls and so a developer has be be very careful about using them as they may be ignored or produce gibberish on many devices. If the book is at all complicated it is vital to test it on as many different devices as possible.