IEC 62541-13:2020 pdf download – OPC Unified Architecture – Part 13: Aggregates.
The TreatUncertainAsBad Variable indicates how the Server treats data returned with a StatusCode severity Uncertain with respect to Aggregate calculations. A value of True indicates the Server considers the severity equivalent to Bad, a value of False indicates the Server considers the severity equivalent to Good, unless the Aggregate definition says otherwise. The default value is True. Note that the value is still treated as Uncertain when the StatusCode for the result is calculated. The PercentDataBad Variable indicates the minimum percentage of Bad data in a given interval required for the StatusCode for the given interval for processed data request to be set to Bad. (Uncertain is treated as defined above.) Refer to 5.4.3 for details on using this Variable when assigning StatusCodes . For details on which Aggregates use the PercentDataBad Variable , see the definition of each Aggregate . The default value is 100. The PercentDataGood Variable indicates the minimum percentage of Good data in a given interval required for the StatusCode for the given interval for the processed data requests to be set to Good. Refer to 5.4.3 for details on using this Variable when assigning StatusCodes . For details on which Aggregates use the PercentDataGood Variable , see the definition of each Aggregate . The default value is 100.
The PercentDataGood and PercentDataBad shall follow the following relationship (100 – PercentDataBad ). If they are equal the result of the PercentDataGood ≥ PercentDataGood calculation is used. If the values entered for PercentDataGood and PercentDataBad do not result in a valid calculation (e.g. Bad = 80; Good = 0) the result will have a StatusCode of Bad_AggregateInvalidInputs The StatusCode Bad_AggregateInvalidInputs will be returned if the value of PercentDataGood or PercentDataBad exceed 100. The UseSlopedExtrapolation Variable indicates how the Server interpolates data when no boundary value exists (i.e. extrapolating into the future from the last known value). A value of False indicates that the Server will use a SteppedExtrapolation format, and hold the last known value constant. A value of True indicates the Server will project the value using UseSlopedExtrapolation mode. The default value is False. For SimpleBounds this value is ignored. 4.2.2 AggregateFunction Object General 4.2.2.1 This Object is used as the browse entry point for information about the Aggregates supported by a Server . The content of this Object is already defined by its type definition. All Instances of the FolderType use the standard BrowseName of ‘AggregateFunctions’. The HasComponent Reference is used to relate a ServerCapabilities Object and/or any HistoryServerCapabilitiesType Object to an AggregateFunction Object . AggregateFunctions is formally defined in Table 3..
4.3 MonitoredItem AggregateFilter 4.3.1 MonitoredItem AggregateFilter Defaults The default values used for MonitoredItem Aggregates are the same as those used for historical Aggregates . They are defined in 4.2.1.2. For additional information on MonitoredItem AggregateFilter see IEC 62541-4. 4.3.2 MonitoredItem Aggregates and Bounding Values When calculating MonitoredItem Aggregates that require the use of Bounding Values , the bounds may not be known. The calculation is done in the same manner as a historical read with the Partial Bit set. The historian may wait some amount of time (normally no more than one processing interval) before calculating the interval to allow for any latency in data collection and reduce the use of the Partial Bit. A historical read done after data collection and the data from the MonitoredItem over the same interval may not be the same. 4.4 Exposing Supported Functions and Capabilities Figure 1 outlines a possible representation of Aggregate information in the AddressSpace . In this example, although the Server at the highest level may support Aggregate functionality for Interpolative, Total, Average, and others, DataVariable X only supports Interpolative, Total and Average, while DataVariable Y supports Average, a vendor defined Aggregate and other (unstated) Aggregates.