[galaxy-dev] retrieving file info from '.dat' dataset

Hi all, I have written a java tool to which I have to pass an existing file's name. In the XML wrapper, I am choosing the file from the history using <param type="data">. Even though the tool is receiving the filename as an input, it is looking for a ".dat" file from \database\000\<some dataset> How do I retrieve the file I need from the dataset? Thanks, VJ.