[igorsk]

Here's a quote from the IEC spec:

DrawChar =
  (element.Plot
   | element.CR
   | element.Fill
   | element.CharButton
   | element.Yoko
   | element.Tate
   | element.Nekase
   | element.NoBR
   | element.DrawChar
   | element.Italic
   | element.Bold
   | SimpleChar1)*
SimpleChar1 =
  (element.Rubi
   | element.Box
   | element.EmpDots
   | element.EmpLine
   | element.Sub
   | element.Sup
   | element.Space
   | SimpleChar0)*
SimpleChar0 = (text | element.Gaiji | element.AltString)*
SimpleChar2 = (element.Plot | SimpleChar0)*