In his previous post, Mike Taulty concentrated on the service side of WCF RIA Services, so he decided that this time he is going to look into the client side. If you have missed the first part of Mike's series, you can catch up here.
From previous investigations we know that a RIA Services client submits 3 fundamental kinds of operations to a RIA services service;
and it’s the DomainClient that knows how to do the client<->server communication for Query, Invoke, Submitasynchronously with cancellation. The DomainContext then is abstracted away from the details of how these operations are transmitted to the server side by relying on the DomainClient to do that work.