anchor.diff:  ;
   
   // ----------------------------------------
  -// ---------- Category attribute ----------
  -// ----------------------------------------
  -
  +// ----------- Category Header ------------
  +// ----------------------------------------
   /*
   ABNF representation of category from the http rendering specification
   
  
positive.code:   PATH
  ;
  
  ATTRIB_NAME: ('a'..'z' | 'A'..'Z')('a'..'z' | 'A'..'Z' | DIGIT)+ ('.') TOKEN;
  PATH: ('/' TOKEN) ('/' TOKEN)*;
  CLASS: ('kind'|'mixin'|'action');
  
negative.code:   CLOSE_PATH = '>';
  }
  
  // ----------------------------------------
  // ---------- All OCCI Headers ------------
  // ----------------------------------------
  
  occi_header:
      category_header
    | link_header
  