Diagram crated by Tom

Each of the orange crosses is an extension point. The pale green boxes represent state (workflow definitions, data values etc) The dark green boxes represent functional units or concerns.

One problem of drawing this is that you always end up drawing a specific configuration. For example, the workflow status monitor could be within the workbench, I've just chosen to have it as a distinct component at the moment. To further confuse things, the workflow status monitor is probably also an implementation of one of the SPIs. (SPI == Service Provider Interface, a mechanism for implementing plugin frameworks). So really it's arbitrary which of the plugins we draw out in detail, I guess we could do it in full for the current workbench but I ran out of space!