cannot access data in incoming xml response message

I have a mystery.  I have worked with integration broker, soap web services, and peopletools document objects for a few years.  I am now programming a process with a CONSUMED REST service - i send the vendor a request for data and they send an xml response.  I created a document to map to the response message.  The problem occurs when I access the response message with the document definition, the data is not recognized.   I can see the data in the raw message but when the peoplecode references the value of each node, the result is zero/null/space.  I have