In the base OPC UA specification, various AuditEvents are defined, each providing specific event fields for particular operations. For example, when a Method is called, an Event of type AuditUpdateMethodEventType may be generated. This EventType already defines fields that describe how the Method was called, such as InputArguments.

If an AuditEvent is required—for example, to record the invocation of a specific Method—either AuditUpdateMethodEventType can be used directly, or a subtype of AuditUpdateMethodEventType can be defined. Creating a subtype allows Events to be categorized more precisely and enables simpler filtering.

Such a subtype should not introduce additional fields, as clients that process OPC UA AuditEvents are generally not capable of handling such extensions. The AuditEvents defined in the base OPC UA specification already provide all relevant information. For example, defining a separate field for a specific Method input argument is unnecessary, since this information is already available through the InputArguments field.

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