The ruby element does not accept any attributes other than the standard ones, such as id , class or style . The rb element is automatically closed by an rt or an rp element. Ruby markup to achieve both top and bottom ruby on the same base. The result of nested ruby markup. The rt element does not allow other nested ruby elements inside of it.
Parentheses are necessary for the ruby to be rendered correctly when it is inline.
The existence of the rp element is necessary especially for UA's that are unable to render ruby text above the ruby base. That way, any ruby will degrade to no worse than a properly formed inline ruby in non-supporting UA's. Glossary Ruby base Run of text that has a ruby text associated with it. Changes from Previous Public Working Draft Section Change Status of This Document mentioned ruby naming and structure control as issues to be discussed at the next WG meeting 1. The rp element removed a mention of specific CSS properties 3.