This Web service acknowledges a concrete event by using its global instance ID.
globalInstanceID: The global instance ID is part of the properties of an event. For more information about how you can query it, see getEventXMLForFilter and handleEvent.
user: This string specifies the user who acknowledges the event. This value can be null to set the default value.
locale: If you want to set the default value, you have to input null. See Localization and input parameters for more information about the locale descriptor.
This Web service returns nothing.