question: public void addAttribute ( String alias , String typeUri , boolean required , int count ) throws MessageException { if ( alias . indexOf ( ',' ) > - 1 || alias . indexOf ( '.' ) > - 1 || alias . indexOf ( ':' ) > - 1 || alias . indexOf ( '\n' ) > - 1 ) throw new MessageException ( "Characters [.,:\\n] are not allowed in attribute aliases: " + alias ) ; _parameters . set ( new Parameter ( "type." + alias , typeUri ) ) ; String level = required ? "required" : "if_available" ; Parameter levelParam = _parameters . getParameter ( level ) ; Parameter newParam ; if ( levelParam == null ) { newParam = new Parameter ( level , alias ) ; } else { newParam = new Parameter ( level , levelParam . getValue ( ) + "," + alias ) ; _parameters . removeParameters ( level ) ; } _parameters . set ( newParam ) ; setCount ( alias , count ) ; if ( DEBUG ) _log . debug ( "Added new attribute to fetch request; type: " + typeUri + " alias: " + alias + " count: " + count + " required: " + required ) ; }
target:  Adds an attribute to the fetch request.