1.8.5 Event Categories
Event categories are integers that are unique on a per-event source basis. The combination of an event source name and an event category suffices to uniquely identify a class of events. Unlike EventIDs, the use of the category is optional (defaulting to 0). Categories are used to group events into broader classes than can be done with EventIDs. For example, an application might use a category for all events that occur during startup, and use another category for events that occur during shutdown. Management applications might use categories to identify what part of the component raised the event.