Ya, I'm having a similiar problem. I found the answer here:
"JAX-RPC 1.1 does not support collections, so you have to use arrays.
The future specification addresses this."
I suppose that this means your soap interface will look somewhat different from other external interfaces that you might be using (ie. RMI) and would require converting the incoming data to your actual type once the rpc call has been made. Anyone with more WS experience care to share on this? Any other ways to deal with this?
The way that guaranties interoperability is to use arrays. It maybe possible to use maps, collections with some java soap stacks, but you will never be sure that the world can actually talk to your endpoint.
JBoss WS4EE does not support collections nor maps.