The container for ruby markup declarations.
               The 
                  its:ruby element contains either 
                  simple or 
                  complex ruby markup.
                  
               
               Refer to 
                  ITS Ruby for further information.
                  
               
             
            Usage Example
    
<p>この本は <its:ruby>
    <its:rb>慶応義塾大学</its:rb>
    <its:rp>(</its:rp><its:rt>けいおうぎじゅくだいがく</its:rt><its:rp>)</its:rp>
</its:ruby>の歴史を説明するものです。</p>
    Allowed parents
            abbr, 
               d:about, 
               address, 
               annoref, 
               annotation (block variant), 
               annotation (phrase variant), 
               m:annotation-xml, 
               aside (block variant), 
               aside (toc variant), 
               block, 
               caption, 
               citation (block variant), 
               citation (phrase variant), 
               code, 
               d, 
               definition, 
               description, 
               emph (phrase variant), 
               emph (text variant), 
               entry (toc variant), 
               entry (index variant), 
               entry (bibliography variant), 
               entry (glossary variant), 
               expansion, 
               h, 
               hd, 
               hpart, 
               item, 
               ln (code variant), 
               ln (ln variant), 
               lnum, 
               d:longdesc, 
               meta, 
               name, 
               note (block variant), 
               note (phrase variant), 
               noteref, 
               num, 
               object, 
               sel:otherwise, 
               p, 
               ssml:phoneme (phrase variant), 
               ssml:phoneme (text variant), 
               ssml:prosody (phrase variant), 
               ssml:prosody (text variant), 
               quote (block variant), 
               quote (phrase variant), 
               its:rb, 
               ref, 
               its:rt, 
               s, 
               ssml:say-as (phrase variant), 
               ssml:say-as (text variant), 
               d:simplifiedLanguageDescription, 
               span (phrase variant), 
               span (text variant), 
               spine, 
               sub, 
               ssml:sub (phrase variant), 
               ssml:sub (text variant), 
               d:summary, 
               sup, 
               td, 
               term, 
               th, 
               time, 
               ssml:token (phrase variant), 
               ssml:token (text variant), 
               d:tour, 
               w, 
               sel:when and 
               wpart
               
            
            Allowed children
            This element must not contain text.
            
            This element may contain the following children: its:rb, 
               its:rbc, 
               its:rp, 
               its:rt and 
               its:rtc
               
            
            Content model
            
               optional attributes: 
@about, 
                  
@by, 
                  
@class, 
                  
@content, 
                  
@continuation, 
                  
@datatype, 
                  
@desc, 
                  
@its:dir, 
                  
@its:translate, 
                  
@property, 
                  
@rel, 
                  
@resource, 
                  
@rev, 
                  
@role, 
                  
@sel:selid, 
                  
@ssml:onlangfailure, 
                  
@typeof, 
                  
@xml:base, 
                  
@xml:id, 
                  
@xml:lang and 
                  
@xml:space 
               a choice of
                  
                  either 
                     
                     
                     
                     followed by 
a choice of 
                        end of choice 
                     
                   
                  
                  
                  end of choice 
               
             
            Namespace
            http://www.w3.org/2005/11/its