DECLARE
  ctx DBMS_XMLGEN.ctxHandle;
  xml CLOB;
BEGIN
  ctx := dbms_xmlgen.newcontext('select * from emp');
  dbms_xmlgen.setrowtag(ctx, 'MY-ROW-START-HERE');
  xml := dbms_xmlgen.getxml(ctx);
  dbms_output.put_line(substr(xml,1,255));
END;
/

ouput returns as below:
   
 <?xml version="1.0"?>
<EMP>
  <EMPNO>7876</EMPNO>
  <ENAME>ADAMS</ENAME>
  <JOB>CLERK</JOB>
  <MGR>7788</MGR>
  <HIREDATE>23-MAY-1987 00:00:00</HIREDATE>
  <SAL>1100</SAL>
  <DEPTNO>20</DEPTNO>
 ...
</EMP>

 
<?xml version="1.0"?>
<EMP>
  <EMPNO>
	<First>78</First>
	<Last>76</Last>
  </EMPNO>
  <ENAME>ADAMS</ENAME>
  <JOB>CLERK</JOB>
  <MGR>7788</MGR>
  <HIREDATE>23-MAY-1987 00:00:00</HIREDATE>
  <SAL>1100</SAL>
  <DEPTNO>20</DEPTNO>
 ...
</EMP> 

SQL> create or replace type empno as object (
  2    first varchar2(2),
  3    last  varchar2(2)
  4    )
  5  /

Type created.

SQL> select dbms_xmlgen.GETXML(
  2  'select empno(substr(empno,1,2),substr(empno,-2)) empno,
  3         ename,job,mgr,hiredate,sal,deptno 
  4  from emp
  5  where empno=7876') val
  6  from dual
  7  /
VAL
--------------------------------------------------------------
<?xml version="1.0"?>
<ROWSET>
 <ROW>
  <EMPNO>
   <FIRST>78</FIRST>
   <LAST>76</LAST>
  </EMPNO>
  <ENAME>ADAMS</ENAME>
  <JOB>CLERK</JOB>
  <MGR>7788</MGR>
  <HIREDATE>23/05/1987 00:00:00</HIREDATE>
  <SAL>1100</SAL>
  <DEPTNO>20</DEPTNO>
 </ROW>
</ROWSET>

1 row selected.