Hi,
Looking at the example on the Tool Config Syntax wiki page:
Assume that the tool includes an input parameter named "database" which is a select list ( e.g., assume the following inputs ):
Assume that the user selects the first option in the $database select list. Then the following will ensure that the tool produces a tabular data set whose associated history item has the label "Blat on Human (hg18)".
1 <outputs>
2 <data format="input" name="output" label="Blat on ${database.value_label}" />
3 </outputs>