A LogObject that supports storing Events as LogRecords extends the behaviour of a LogObject by providing the capability to collect all Events that the parent Object receives that have a ConditionClassId or SubConditionClassId of LogEntryConditionClass.

For example, since Events / Conditions / Alarms instance can be defined by PLC programs and exposed in a Server, the LogObject can collect Diagnostics or other trace information from PLC user program, not just from Server code.

The LogObject can utilize some of the Event reporting hierarchy concepts defined in OPC 10000-3 and OPC 10000-5. Figure 5 illustrates a Server that includes an Event hierarchy. In the example, LogObjectArea2 would include all Events that would be available from the Area2 Object that have a ConditionClassId or ConditionSubClassId of LogEntryConditionClass. In addition the LogObject could store additional fields from Events in the AdditionalData NameValue pairs. What fields are be stored would be vendor / Server specific, but specifications that define LogObject instances may also define additional fields from defined Events that shall be stored in a LogRecord.

Figure 5 – LogObject Event usage illustration