I tried concat(/process_data/@checkit,string-length(/process_data/@checkit) > 0).
What I ended up with was "addressTRUE" for the value in the address2 field.
I might not be doing what you intended.
I see how to test the string length and get a boolean value, but I need to move the city, state and zip into the address2 field if address2 is null.
Thanks.