cmTrapEventLogObjectClass is a read-only enumeration identifying what kind of resource (system, shelf, a specific board type, and so on) generated a given event-log entry. An administrator uses it to filter the event log down to a resource category, such as isolating all board-related events from shelf- or system-level ones. For example, filtering on a specific brd* class would let the operator see only events generated by that type of line card across the chassis.