In WebSphere Process Server: A Russian Doll, I showed how WPS contains WESB, which contains WAS. Here's a better picture of that:
WebSphere Application Server, ESB, and Process Server
In WebSphere Process Server Components, I showed the component architecture in WPS. That picture changed a little when we released WESB, which WPS is now built on. Here's the updated picture:
WebSphere integration product family
Actually, I disagree with this picture a little bit. I think we should show the Mediation Flows box as its own row above SOA Core and below Supporting Services. Then you could draw a line between Mediation Flows and Supporting Services and say that everything below the line is in WESB, whereas the stuff above the line what WPS adds. In other words, WESB has Mediation Flows, but doesn't have anything else in the Supporting Services row; I wish the picture showed that better.
Way back in December, in Service Component Architecture, I showed what an SCA looks like and how it can be implemented. Here's an update:
Service Component Architecture overview
I like the way this picture shows both the Interface and the Reference(s). Other versions of this diagram I've seen show Selector and Interface Maps separated from the rest of the Implementation list; this is because those latter two don't really implement anything, they're adapters for connecting to an existing implementation. Too bad this version doesn't show that detail.
So, I hope these updated diagrams help you understand what I've been talking about a little better. Enjoy.