Check a field exists in the XML with BI Publisher

this turned in to a bit of a GOTYA!  we had an interesting issue where mike was using a language field to control how a field looked on the page.  the trouble was we occasionally got crap data where the language field had not been populated  and the default section in a choose statement wasn't firing

the solution turned out to be

<?if:not(element_name)?> desired behavior when the element is not present <?end if?>

 which fixed the problem nicely  thank you google we love you !!!!!!!