GWT Application consumming webservices from DFS

Hi all, my name is Ignacio and i have a cuestion

I'm developing a GWT app wich "talk" with Documentum to manage stored files on it . Requests from gwt client to gwt server uses REST to indicate what user wants to do.

Example:

GWT client ->(how much documents exists?)-> GWT server -> (how much documents exists?) -> Documentum

Documentum ->(12)-> GWT server -> (12) -> GWT client

My cuestion is: there are any way to do this proces but using DFS (Web services)?

I read a lot of webs where talk about use webservicies in GWT using JSON and REST. But it isn't what i want, because all what use REST needs a server.

So, it would be posible:

GWT client -> (use web service: how much documents exist?) -> DFS

DFS -> (XML or JSON : 12) -> GWT Client

Thanks a lot!

Ignacio