Greetings, I have a question about setting up an external data source. My case should be fairly simple - The external data source's URL requires no parameters, and when the data is returned, it's just a URL directly to a file. Example: http://myserver/data_search_page.html returns... http://myserver/repository/the_file.bed I've looked at multiple examples of the XML files & the wiki, and I think I've got it. However there's one part I'm still unclear about - the <param> tag inside the <inputs> tag. Examples: <param name="GALAXY_URL" type="baseurl" value="/tool_runner/biomart" /> <param name="GALAXY_URL" type="baseurl" value="/tool_runner" /> <param name="GALAXY_URL" type="baseurl" value="/tool_runner?tool_id=flymine" /> It seems that the "value" string gets appended onto the GALAXY_URL (which would then be returned to Galaxy). Could you please explain what's happening here? Do I need to write a separate tool which would be executed by 'tool_runner'? I thought "data_source.py" *was* the tool, no? Thanks very much for your help, Chris Zaleski Gingeras Lab - CSHL