| interface  | Category | Event annotation, to associate the event type with a category, in the format
 of a human-readable path. | 
| interface  | Enabled | Event annotation, determines if an event should be enabled by default. | 
| interface  | Experimental | Annotation that specifies that an element is experimental and may change
 without notice. | 
| interface  | Period | Event annotation, specifies the default setting value for a periodic event. | 
| interface  | Registered | Event annotation, for programmatic event registration. | 
| interface  | StackTrace | Event annotation, determines whether an event by default has a stack trace
 or not. | 
| interface  | Threshold | Event annotation, specifies the default duration below which an event is not
 recorded (for example, "20 ms"). |