For transferring data between heterogeneous databases, XML is becoming a method of choice. While deployment is generally successfully, there are barriers to overcome. A recent example at NLM involved transfers between "DCMS" and "Mars". These two document workflow systems, with separate databases, process biomedical journals for incorporation into NLM's "MEDLINE". DCMS acts as an overall manager, while Mars is one of three decoupled methods for harvesting the abstracts and citation information from articles. A preexisting flow of article information from the "back end" of Mars was first recast into XML for delivery to DCMS by an "Upload" daemon. Next addressed was the lack of data flow from DCMS to the Mars "front end", necessitating duplicative data entry by Mars operators. The desired flow was achieved as XML, mediated by a new "CheckIn" module. Bumps hit on the road to successful deployment of these transfer...