Deal all, We have a tool with the following parameters declarations: <inputs> <param type="data" format="tabular, csv" name="input" required="True" label="Please select the file to read" help = " This tools only supports comma separated (.csv, .txt) and tab separated (.tab, .txt) text files. If you can't see your file in the selection box make sure that you have uploaded it using the correct file format. Alternatively, you can convert almost any character separated text file in to tab separated using the 'Convert delimiters to TAB' tool (under 'Text Manipulation')"/> <param name="idcol" label="Column containing a unique ID for each compound" type="data_column" data_ref="input" accept_default="true" help = "Your file must contain at least one column with a unique ID for each compound."/> <param name="columnList" label="Columns containing property values" type="data_column" data_ref="input" accept_default="true" multiple="true" display="checkboxes" force_select = "false" help = "Your file can contain columns that describe more that one properties. Select all the columns you want to read here."/> <param name="outcol" label="Column containing an outcome value" type="data_column" data_ref="input" accept_default="true" help = "If your file contains a column that describe the outcome of an experiment you should select it here. Currently only one outcome per file is supported."/> </inputs> As you can see in the highlighted lines, we have a parameter that is of type data_column and has data_ref the input dataset, also allows multiple selection. The purpose is to have a multiple selection of columns from the input file. But in the interface we see a '?' as first column and then the columns of the input file. If we remove the multiple select its ok. Does data_ref works along side multiple selection? Regards, Christos -- Christos Kannas Researcher Ph.D Student e-Health Laboratory <http://www.medinfo.cs.ucy.ac.cy/> kannas.christos@ucy.ac.cy kannas.christos@cs.ucy.ac.cy chriskannas@gmail.com Mob: (+357) 99530608