Windows State Machine workflow: How can we achieve Parent Child workflow communication when both are hosted as WF service.

Question

I am trying to spawn child workflows as services from parent workflow which is also a workflow hosted as a service.

Problems I am facing:

1. How to spawn multiple child workflows as service "synchronously"?
2. How to communicate to the consuming applications that the child workflows are ready for action?
3. How to communicate to the parent that a child workflow is complete "synchronously"?

Thanks.