I very recently started working on ADF BC based webservices and had to create a web service in which I can pass a master detail stuff.
After generating the client proxy I could see the parent VO SDO but it was missing the child VO SDO to pass child details. So, in such situations the most obvious place to look for is the parent xsd generated by jdeveloper. I looked into it and to my surprise the child vo details were not included in the parent vo xsd.
I retried the process of generating the service interface of my application module number of times and every time it failed to generate the child vo details in the parent vo xsd. The natural thing came to my mind was a bug in jdeveloper in this case. I was about to do that and by chance I just navigated to child VO details and saw that child vo is not exposed as a service. So, I manually did that and bingo!!! The smart jdeveloper automatically updated my parent vo xsd to include its details.
So, I would conclude it saying that when I generated the service interface for my AM at that time while including parent vo it should automatically take care to generate the child vo xsd as well.