Service Component Architecture


So yet again I think I must be stupid because I don’t understand the whole Service Component Architecture thing. It looks like a programming model (e.g. set of API's) to build web services. I thought that’s one of the many things that J2EE was meant to be supplying. Anyway Microsoft already has that with Windows Communication Framework (WCF) so what's the big deal? Why do we need yet another way of calling web services?