This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
That would mean, I think, that no ancestor of that element declares a namespace for which DbGML is the prefix. Look in your XML for namespace declarations. And make sure your parser is set up to be namespace-aware (although it probably is).