Approved May 8, 2021 by the Technical Committee of Japan DAISY Consortium
This document summarizes discovery requirements for accessible EPUB publications according to user preferences on ruby presentations. It is hoped that this document helps to introduce ruby metadata to Schema.org and ONIX and that such ruby metadata become usable from EPUB Accessibility of ISO/IEC.
Terms (most notably “discovery”) defined in EPUB Accessibility (ISO/IEC 23761 and W3C Member Submission) and the following terms apply.
Some persons find it difficult to read CJK ideographic characters. Some of these persons are not dyslexic but do not know CJK ideographic characters well. Others are dyslexic such that complicated CJK ideographic characters look like black squares.
Note: Japanese students learn 2136 CJK ideographic characters in the period of compulsory education. In Mainland China, Hong Kong, Macau, and Taiwan, students must learn more.
Ruby has been a traditional remedy to such persons. The general-ruby method is preferable to those who have significant problems with CJK ideographic characters. Meanwhile, the para-ruby method is often good enough.
Note: CSS properties for controlling ruby can be enabled or disabled depending on classes attached to ruby elements. For this reason, it is possible to create an EPUB publication whose ruby can be rendered differently: the general-ruby method, the para-ruby method, or no ruby. Thus, the same document may be found by a query for general-ruby as well as a query for para-ruby.
Although ruby helps some persons, it disturbs others. Specifically, some dyslexic persons find it difficult to distinguish ruby and base text to which ruby is attached. They mistakenly assume the combination of ruby and base text as a single gigantic character.
One of the remedies is to hide ruby. Fortunately, ruby in any EPUB publication can be hidden by invoking an appropriate CSS stylesheet (i.e., display: none for rt elements)
Another remedy is to use different color for ruby. Yet another is to widen the gap between ruby and base text. Again, both remedies are possible for any EPUB publication by invoking appropriate CSS stylesheets.
Mimicking ruby in source publications is useful for two reasons. First, even those who need general-ruby inthe first step are, in the second step, wiling to try what others read.
Second, some persons with or without print disabilities do not have any special requirements on ruby. They are willing to use EPUB publications that can faithfully mimic ruby in source (typically printed) publications.