A target Pin can only be owned by a CallOperationAction or a SendSignalAction.
The target Pin is an InputPin that represents the target object to which the request or signal is sent. Only CallOperationActions or SendSignalActions can own such a Pin.
This rule is triggered when the “Self” property of a Pin is checked and the owner of the Pin in question is neither a CallOperationAction nor a SendSignalAction.
This property can be modified through the “Element” view when the Pin is selected.