XMLElement in BI Publisher SQL Query

Hi. 

In Oracle BI Publisher 11.1.1.9 I'm creating a dataset by writing this simple query:

select XMLELEMENT ("Detail",

      XMLELEMENT("Bill To",BILL_TO_CUSTOMER_ID),

      XMLELEMENT("TRX ID",CUSTOMER_TRX_ID)) as DETAIL FROM RA_CUSTOMER_TRX_ALL

WHERE CUSTOMER_TRX_ID = 300000003069790

Of course, data exist. A blank output comes after pressing the "View" button.

Do I need any setting or privilege or role or anything else?

Thank you

Best Regards

Vincenzo