EPUB does not define a method for including translations

[gautierchomel]

Issue on the EPUB 3.3 Recommendation

Missing part of the recommendation.

Describe the problem

Content creators producing EPUBs with different languages for the same content in a unique file have no guidance on how to do it. Reading system developers have no advice on handling multiple metadata with different lang attributes.

This has been discussed previously in Add a "translation" value to the refines mechanism #1553. Still, the resolutions seem insufficient has it appeared more recently in How to write the OPF of a book containing two or more translations of the same work? #47 and appears again when we try to define how to parse multiple accessibility summaries that are not exactly forbidden, even if a content creator digging to Section 3.6 of the accessibility techniques will find this warning:

Do not repeat this property to provide translations of a summary. EPUB does not define a method for including translations. Putting different xml:lang attributes on properties does not indicate a translation and could lead to the wrong summary being rendered to users.

Describe the fix or new feature you propose

Defining how to inform translation inside an epub would remove ambiguity even if reading systems ignore the translations. It also shouldn’t introduce any complications for existing metadata since it could be a refine of another property and would have a name unknown to existing reading systems.