When an ExecutableNode completes an execution, the control token representing that execution is removed from the ExecutableNode and control tokens are offered on all outgoing ControlFlows of the ExecutableNode. That is, there is an implicit fork ... Source Unified Modeling Language 2.5.1
In some cases, multiple concurrent executions of an ExecutableNode may be ongoing at one time (see the semantics of isLocallyReentrant=true for Actions ... ). In this case, the ExecutableNode holds one control token for each concurrent execution. Source Unified Modeling Language 2.5.1
While the ExecutableNode is executing, it is considered to hold a single control [token] indicating it is execution [executing]. Source Unified Modeling Language 2.5.1
The effect of object tokens accepted from ControlFlows is not specified (see isControlType for ObjectNodes ...), but the semantics above applies if the effect is to execute the ExecutableNode. Source Unified Modeling Language 2.5.1
Before an ExecutableNode begins executing, it accepts all tokens offered on incoming ControlFlows. If multiple tokens are being offered on a ControlFlow, they are all consumed. Source Unified Modeling Language 2.5.1
An ExecutableNode shall not execute until all incoming ControlFlows (if any) are offering tokens. That is, there is an implicit join on the incoming Control Flows. Specific kinds of ExecutableNodes may have additional prerequisites ... Source Unified Modeling Language 2.5.1
