Hi, I am trying to write a tool xml file and want to do the following: I have a number of GTF files stored locally and referenced in a data table. I give the user a drop down list of those available using the following code: <param name="gtf" type="select" label="GTF File"> <options from_data_table="gtf_files"/> </param> I then want them to choose an annotation type based on those present in the selected gtf file above. It seems simple enough to do this if the gtf file is in your history already: <param name="feature" type="select" multiple="true" label="Extract features"> <options from_dataset="gtf"> <column name="name" index="2"/> <column name="value" index="2"/> <filter type="unique_value" name="unique" column="2"/> </options> </param> But is there a way to query locally stored files via datatables/.loc files to pull out options when the file is dynamically chosen by a different parameter? This code is also wrapped in a conditional, I'm not sure if that will affect anything. Thanks Shaun -- The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336.