Begin forwarded message:

In theory, the correct attribute should be "$input1.extension". Let us know if that doesn't work though.

Hi Belinda, The condition you want to use is this: #if isinstance( $input1.datatype, $__app__.datatypes_registry.get_data type_by_extension('interval').__class__): You can see this example in context by looking at the XML tool definition file for the intersect tool, intersect.xml Let us know if this doesn't solve your problem. Best, J.