Calling a database pkg function from the data template

Hello,

I  have the following sqlStatement in my data template:

<sqlStatement name="Q_SEL">
<![CDATA[ Select xla_tb_ap_report_pvt.get_period_name(1) PERIOD_NAME
from dual]]>
</sqlStatement>

My group is :
<group name="G_PERIOD_NAME" source="Q_SEL">
<element name="PERIOD_NAME" value="PERIOD_NAME"/>
</group>

Getting the error message:
ORA-00904: xla_tb_ap_report_pvt.get_period_name : invaild identifier

What is it that i am doing wrong?

Thanks,

Monkey