Hi, Gerrit, For general information of typesetting Japanese (modern) texts, there is a standard (in English) publicly available at W3G[1].
[1] "Requirements for Japanese Text Layout" http://www.w3.org/TR/jlreq/ Best regards, -- Ryo IGARASHI, Ph.D. rigar...@gmail.com -------------------------------------------------- Subscriptions, Archive, and List information, etc.: http://tug.org/mailman/listinfo/xetex
