Null tags in XML

Hi,

I have few null tags in the XML file which is showing presented as below:

<TAX_CODE/>

Now my requirement is to put a check whether the TAX_CODE is null based on which a group is to be displayed.

I have gone through the Oracle docs(Creating an RTF Template) and tried with the code

<?if:TAX_CODE and TAX_CODE="?> desired behavior <?end if?>

but it is not working.

But after explicitly putting the value 'null' in the XML file , when I am using <?if:TAX_CODE='null'?> , it is working.