A running invocation (see SCXMLSession.invocations).
SCXMLSession.invocations
The invocation's id.
The <invoke> itself.
<invoke>
Optional
The child session, for SCXML invocations.
The state whose <invoke> started it.
The invoke type (the SCXML type URI or a custom invoker's name).
A running invocation (see
SCXMLSession.invocations).