Implementing observer pattern using WCF

Question

When I first posted this question I had strong coupling between my web service and application controller where the controller needed to open multiple threads to the service and

Answer 1

I'm not so sure that duplex is needed here... IMO, a standard async call with a callback should be more than sufficient to get notification of data delivery.

What is the biggest problem? If you are talking about async etc, then usually we are talking about the time taken to get the data to the client. Is this due to sheer data volume? or complexity generating the data at the server?

If it is the data volume, then I can think of a number of ways of significantly improving performance - although most of them involve using DTO objects (not DataSet/DataTable, which seemed to be implied in the question). For example, protobuf-net significantly reduces the data volume and processing required to transfer data.