More documentation needed here!
Set values in the RuleInputField can be preprocessed. At now you can specify a processor class to pre process a value to be set at initial value of a RuleInputField. Syntax:
<spec set="0:defaultVal:classname" .../>
The class name is an optional value. The class must implement the Processor interface.
You can specify a processor for a combobox:
<choice processor="fully.qualified.class.name"
set="selectedValue"/>
so that you can fill a combobox with data on a simple way.