| key | 
                                 xs:string | 
                                  | 
                                  | 
                                 optional | 
                                  | 
                                 
                                    
                                       
                                          
                                             provides an externally-defined means of identifying the entity (or
entities) being named, using a coded value of some kind.  | 
                                           
                                        
                                     
                                  | 
                              
                              
                                 | nymRef | 
                                 restriction of list of xs:anyURI | 
                                  | 
                                  | 
                                 optional | 
                                  | 
                                 
                                    
                                       
                                          
                                             (reference to the canonical name) provides a means of locating the
canonical form (nym) of the names associated with the object named by the element bearing
it.  | 
                                           
                                        
                                     
                                  | 
                              
                              
                                 | ref | 
                                 restriction of list of xs:anyURI | 
                                  | 
                                  | 
                                 optional | 
                                  | 
                                 
                                    
                                       
                                          
                                             (reference) provides an explicit means of locating a full definition or
identity for the entity being named by means of one or more URIs.  | 
                                           
                                        
                                     
                                  | 
                              
                              
                                 | role | 
                                 restriction of list of restriction of xs:token | 
                                  | 
                                  | 
                                 optional | 
                                  | 
                                 
                                    
                                       
                                          
                                             may be used to specify further information about the entity referenced by
this name in the form of a set of whitespace-separated values, for example the occupation
of a person, or the status of a place.  | 
                                           
                                        
                                     
                                  |