Hello Galaxy folks I'm building a tool to run the Trimmomatic program, and I've encountered an issue with filtering options from an external .loc file based on the value of a parameter which is defined within a conditional block. The parameter definition looks like this: ... <conditional name="paired_end"> <param name="is_paired_end" type="boolean" label="Paired end data?" truevalue="yes" falsevalue="no" checked="on" /> <when value="no"> ... Subsequently I try to access the value of "is_paired_end" within a filter tag (to select a subset of items from a .loc file), using "ref_attribute" (based on the assumption that I'm trying to access "paired_end.is_paired_end"): ... <options from_file="adapters.loc"> <filter type="param_value" column="1" ref="paired_end" ref_attribute="is_paired_end" /> ... However this doesn't work, in that no options are returned by the filter. A debug statement in the relevant code for the ParamValueFilter (in dynamic_options.py) tells me that there's no "is_paired_end" attribute. The only other tool I could find which uses "ref_attribute" is bfast_wrapper.xml, but this is accessing the "extension" attribute of a parameter not within a conditional (i.e. not the same as my example). Should it be possible to do what I'm trying? Or is there a different way to do it? Thanks for any help or suggestions, Best wishes Peter -- Peter Briggs peter.briggs@manchester.ac.uk Bioinformatics Core Facility University of Manchester B.1083 Michael Smith Bldg Tel: (0161) 2751482