Sources of Events Events may originate within Horizon itself or from outside. Internally-generated events can be the result of the platform’s monitoring and management functions (e.g. a monitored node becoming totally unavailable results in an event with the UEI uei.opennms.org/nodes/nodeDown) or they may act as inputs or outputs of housekeeping processes. The following subsections summarize the mechanisms by which externally created events can arrive. Events SNMP Traps