Specifying inputs and outputs for Modeler steps

Consider a situation where a process has a receive step and then it has a flow step that does simple mapping between input and output(Just String) and then i have a reply step.

in the webmethods advantage site , there is as example just like this , and that example runs fine.

I tried the same thing myself, i got an exception while executing the process, the error occurs because the input and output mappings are not proper.

In the sense, in the advantage example, inputs and ouputs are shown for every step, in my case its happening only for inputs. i.e my recive steps takes a document but doesnt return that document to the next step, that is a flow step.

The problem is that i am not able to map both inputs and outputs.

Can you please help me out, thanks in advance.