BCP 47 is described at https://tools.ietf.org/html/bcp47. The IANA Subtag Registry, from which BCP 47 language tags are constructed, may be found at www.iana.org/assignments/language-subtag-registry. A tool for locating subtags and validating language tags is available at https://r12a.github.io/apps/subtags.
                     <classSpec ident="att.lang" module="MEI.shared" type="atts">
                        
                        <desc>Language attributes common to text elements.</desc>
                        
                        <attList org="group">
                           
                           
                           <attDef ident="xml:lang" usage="opt">
                              
                              <desc>Identifies the language of the element's content. The values for this attribute are
                                 language 'tags' as defined in BCP 47. All language tags that make use of private use
                                 sub-tags must be documented in a corresponding language element in the MEI header
                                 whose id
                                 attribute is the same as the language tag's value.</desc>
                              
                              <datatype maxOccurs="1" minOccurs="1">
                                 
                                 <rng:data type="language"/>
                                 </datatype>
                              </attDef>
                           
                           <attDef ident="translit" usage="opt">
                              
                              <desc>Specifies the transliteration technique used.</desc>
                              
                              <datatype maxOccurs="1" minOccurs="1">
                                 
                                 <rng:data type="NMTOKEN"/>
                                 </datatype>
                              
                              <remarks>
                                 
                                 <p part="N">There is no standard list of transliteration schemes.</p>
                                 </remarks>
                              </attDef>
                           </attList>
                        
                        <remarks>
                           
                           <p part="N">BCP 47 is described at 
                              <ref target="https://tools.ietf.org/html/bcp47">https://tools.ietf.org/html/bcp47</ref>. The IANA Subtag Registry, from which BCP 47
                              language tags are constructed, may be found at 
                              <ref target="www.iana.org/assignments/language-subtag-registry">www.iana.org/assignments/language-subtag-registry</ref>. A tool for locating subtags and
                              validating language tags is available at 
                              <ref target="https://r12a.github.io/apps/subtags">https://r12a.github.io/apps/subtags</ref>.</p>
                           </remarks>
                        </classSpec>