This report defines one set of property values for interchange, and recommend higher-level protocols to tailor to match to their preferred style. The current proposed draft states this.
The orientation of many western origin letters and symbols can take two directions, upright or sideways, depending on it's position.
As the result, one set of property values is not enough to interchange the orientation of each characters within Japanese vertical writing effectively. If we use only one set of default orientation, it will be necessary to rotate the "different from default" orientation of characters at position by position. Thousands of mark up will be necessary in some kind of book.
It needs two default sets, SVO-like and MVO-like, for the purpose of interchange of qualified vertical style information effectively.
Antenna House, Inc.