SQL> CREATE TABLE elements ( parameter_name   VARCHAR2(10),
  2                          parameter_type   VARCHAR2(10),
  3                          parameter_value  VARCHAR2(10) )
  4  /

Table created.

SQL> INSERT INTO elements VALUES ( 'ELEMENT1', 'TYPE1', 'VALUE1' )
  2  /

1 row created.

SQL> 
SQL> INSERT INTO elements VALUES ( 'ELEMENT2', 'TYPE2', 'VALUE2' )
  2  /

1 row created.

SQL> CREATE OR REPLACE FUNCTION get_xml ( p_name IN VARCHAR2,
  2                                       p_type IN VARCHAR2,
  3                                       p_value IN VARCHAR2 )
  4    RETURN XMLTYPE
  5  AS
  6    x  XMLTYPE;
  7  BEGIN
  8    EXECUTE IMMEDIATE 
  9    'SELECT XMLELEMENT("' || p_name || '", ' ||
 10                                         'XMLATTRIBUTES(:1 "type"), :2) FROM dual' 
 11                       INTO x
 12                      USING p_type, p_value;
 13    RETURN x;
 14  END get_xml;
 15  /

Function created.

SQL> SELECT 
  2    XMLAGG(get_xml(e.parameter_name, e.parameter_type, e.parameter_value))
  3  FROM 
  4    elements e
  5  /

XMLAGG(GET_XML(E.PARAMETER_NAME,E.PARAMETER_TYPE,E.PARAMETER_VALUE))
----------------------------------------------------------------------------------------
<ELEMENT1 type="TYPE1">VALUE1</ELEMENT1><ELEMENT2 type="TYPE2">VALUE2</ELEMENT2>

1 row selected.