UA Part 13: Aggregates - 4 Aggregate information model

OPC 10000-3 and OPC 10000-5 standards define the representation of Aggregate historical or buffered real time data in the OPC Unified Architecture. This includes the definition of Aggregates used in processed data retrieval and in historical retrieval. This definition includes both standard Reference types and Object types.

4.2 Aggregate Objects

4.2.1 General

4.2.1.1 Overview

OPC UA Servers can support several different functionalities and capabilities. The following standard Objects are used to expose these capabilities in a common fashion, and there are several standard defined concepts that can be extended by vendors.

4.2.1.2 AggregateConfigurationType

The AggregateConfigurationType defines the general characteristics of a Node that defines the Aggregate configuration of any Variable or Property. AggregateConfiguration Object represents the browse entry point for information on how the Server treats Aggregate specific functionality such as handling Uncertain data. It is formally defined in Table 2.

Table 2 – AggregateConfigurationType Definition

Attribute	Value
BrowseName	AggregateConfigurationType
IsAbstract	False
References	NodeClass	BrowseName	DataType	TypeDefinition	ModellingRule
Subtype of the BaseObjectType defined in OPC 10000-5
HasProperty	Variable	TreatUncertainAsBad	Boolean	PropertyType	Mandatory
HasProperty	Variable	PercentDataBad	Byte	PropertyType	Mandatory
HasProperty	Variable	PercentDataGood	Byte	PropertyType	Mandatory
HasProperty	Variable	UseSlopedExtrapolation	Boolean	PropertyType	Mandatory
Conformance Units
Aggregate Master Configuration

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 following calculations are used to detemine the StatusCode which will be used to calculate the value of the aggregate. Refer to 5.4.3 for details on using these Variables when assigning StatusCodes. The PercentDataGood and PercentDataBad shall follow the following relationship PercentDataGood ≥ (100 – PercentDataBad). If they are equal the result of the 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

4.2.2.1 General

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.

Table 3 – Aggregate Functions Definition

Attribute	Value
BrowseName	AggregateFunctions
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	FolderType	Defined in OPC 10000-5
Conformance Units
Historical Access Aggregates

Each ServerCapabilities and HistoryServerCapabilitiesType Object shall reference an AggregateFunction Object. In addition, each HistoricalConfiguration Object belonging to a HistoricalDataNode may reference an AggregateFunction Object using the HasComponent Reference.

4.2.2.2 AggregateFunctionType

This ObjectType defines an Aggregate supported by a UA Server. This Object is formally defined in Table 4.

Table 4 – AggregateFunctionType Definition

Attribute	Value
BrowseName	AggregateFunctionType
IsAbstract	False
References	Node Class	BrowseName	DataType	TypeDefinition	Mod.Rule
Subtype of the BaseObjectType defined in OPC 10000-5
Conformance Units
Historical Access Aggregates

For the AggregateFunctionType, the Description Attribute (inherited from the Base NodeClass), is mandatory. The Description Attribute provides a localized description of the Aggregate.

Table 5 specifies the BrowseName and Description Attributes for the standard Aggregate Objects. The description is the localized “en” text. For other locales it shall be translated.

Table 5 – Standard AggregateType Nodes

BrowseName	Description
Interpolative	At the beginning of each interval, retrieve the calculated value from the data points on either side of the requested timestamp.
Average	Retrieve the average value of the data over the interval.
TimeAverage	Retrieve the time weighted average data over the interval using Interpolated Bounding Values.
TimeAverage2	Retrieve the time weighted average data over the interval using Simple Bounding Values.
Total	Retrieve the total (time integral) of the data over the interval using Interpolated Bounding Values.
Total2	Retrieve the total (time integral) of the data over the interval using Simple Bounding Values.
Minimum	Retrieve the minimum raw value in the interval with the timestamp of the start of the interval.
Maximum	Retrieve the maximum raw value in the interval with the timestamp of the start of the interval.
MinimumActualTime	Retrieve the minimum value in the interval and the timestamp of the minimum value.
MaximumActualTime	Retrieve the maximum value in the interval and the timestamp of the maximum value.
Range	Retrieve the difference between the minimum and maximum value over the interval.
Minimum2	Retrieve the minimum value in the interval including the Simple Bounding Values.
Maximum2	Retrieve the maximum value in the interval including the Simple Bounding Values.
MinimumActualTime2	Retrieve the minimum value with the actual timestamp including the Simple Bounding Values.
MaximumActualTime2	Retrieve the maximum value with the actual timestamp including the Simple Bounding Values.
Range2	Retrieve the difference between the Minimum2 and Maximum2 value over the interval.
Count	Retrieve the number of raw values over the interval.
DurationInStateZero	Retrieve the time a Boolean or numeric was in a zero state using Simple Bounding Values.
DurationInStateNonZero	Retrieve the time a Boolean or numeric was in a non-zero state using Simple Bounding Values.
NumberOfTransitions	Retrieve the number of changes between zero and non-zero that a Boolean or numeric value experienced in the interval.
Start	Retrieve the value at the beginning of the interval.
End	Retrieve the value at the end of the interval.
Delta	Retrieve the difference between the Start and End value in the interval.
StartBound	Retrieve the value at the beginning of the interval using Simple Bounding Values.
EndBound	Retrieve the value at the end of the interval using Simple Bounding Values.
DeltaBounds	Retrieve the difference between the StartBound and EndBound value in the interval using Simple Bounding Values.
DurationGood	Retrieve the total duration of time in the interval during which the data is Good.
DurationBad	Retrieve the total duration of time in the interval during which the data is Bad.
PercentGood	Retrieve the percentage of data (0 to 100) in the interval which has Good StatusCode.
PercentBad	Retrieve the percentage of data (0 to 100) in the interval which has Bad StatusCode.
WorstQuality	Retrieve the worst StatusCode of data in the interval.
WorstQuality2	Retrieve the worst StatusCode of data in the interval including the Simple Bounding Values.
AnnotationCount	Retrieve the number of Annotations in the interval (applies to Historical Aggregates only).
StandardDeviationSample	Retrieve the standard deviation for the interval for a sample of the population (n-1).
VarianceSample	Retrieve the variance for the interval as calculated by the StandardDeviationSample.
StandardDeviationPopulation	Retrieve the standard deviation for the interval for a complete population (n) which includes Simple Bounding Values.
VariancePopulation	Retrieve the variance for the interval as calculated by the StandardDeviationPopulation which includes Simple Bounding Values.

4.2.2.3 Interpolative Aggregate Object

The Interpolative Aggregate Object is an instance of AggregateFunctionType and represents the interpolative aggregate function defined in 5.4.3.4. See Table 8 for details.

Table 6 – Interpolative Aggregate Object

Attribute	Value
BrowseName	Interpolative
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - Interpolative

4.2.2.4 Average Aggregate Object

The Average Aggregate Object is an instance of AggregateFunctionType and represents the average aggregate function defined in 5.4.3.5. See Table 7 for details.

Table 7 – Average Aggregate Object

Attribute	Value
BrowseName	Average
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - Average

4.2.2.5 TimeAverage Aggregate Object

The TimeAverage Aggregate Object is an instance of AggregateFunctionType and represents the time average aggregate function defined in 5.4.3.6. See Table 8 for details.

Table 8 – TimeAverage Aggregate Object

Attribute	Value
BrowseName	TimeAverage
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - TimeAverage

4.2.2.6 TimeAverage2 Aggregate Object

The TimeAverage2 Aggregate Object is an instance of AggregateFunctionType and represents the time average 2 aggregate function defined in 5.4.3.7. See Table 9 for details.

Table 9 – TimeAverage2 Aggregate Object

Attribute	Value
BrowseName	TimeAverage2
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - TimeAverage2

4.2.2.7 Total Aggregate Object

The Total Aggregate Object is an instance of AggregateFunctionType and represents the total aggregate function defined in 5.4.3.8. See Table 10 for details.

Table 10 – Total Aggregate Object

Attribute	Value
BrowseName	Total
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - Total

4.2.2.8 Total2 Aggregate Object

The Total2 Aggregate Object is an instance of AggregateFunctionType and represents the total 2 aggregate function defined in 5.4.3.9. See Table 11 for details.

Table 11 – Total2 Aggregate Object

Attribute	Value
BrowseName	Total2
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - Total2

4.2.2.9 Minimum Aggregate Object

The Minimum Aggregate Object is an instance of AggregateFunctionType and represents the minimum aggregate function defined in 5.4.3.10. See Table 12 for details.

Table 12 – Minimum Aggregate Object

Attribute	Value
BrowseName	Minimum
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - Minimum

4.2.2.10 Maximum Aggregate Object

The Maximum Aggregate Object is an instance of AggregateFunctionType and represents the maximum aggregate function defined in 5.4.3.11. See Table 13 for details.

Table 13 – Maximum Aggregate Object

Attribute	Value
BrowseName	Maximum
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - Maximum

4.2.2.11 MinimumActualTime Aggregate Object

The MinimumActualTime Aggregate Object is an instance of AggregateFunctionType and represents the minimum actual time aggregate function defined in 5.4.3.12. See Table 14 for details.

Table 14 – MinimumActualTime Aggregate Object

Attribute	Value
BrowseName	MinimumActualTime
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - MinimumActualTime

4.2.2.12 MaximumActualTime Aggregate Object

The MaximumActualTime Aggregate Object is an instance of AggregateFunctionType and represents the maximum actual time aggregate function defined in 5.4.3.13. See Table 15 for details.

Table 15 – MaximumActualTime Aggregate Object

Attribute	Value
BrowseName	MaximumActualTime
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - MaximumActualTime

4.2.2.13 Range Aggregate Object

The Range Aggregate Object is an instance of AggregateFunctionType and represents the range aggregate function defined in 5.4.3.14. See Table 16 for details.

Table 16 – Range Aggregate Object

Attribute	Value
BrowseName	Range
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - Range

4.2.2.14 Minimum2 Aggregate Object

The Minimum2 Aggregate Object is an instance of AggregateFunctionType and represents the minimum 2 aggregate function defined in 5.4.3.15. See Table 17 for details.

Table 17 – Minimum2 Aggregate Object

Attribute	Value
BrowseName	Minimum2
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - Minimum2

4.2.2.15 Maximum2 Aggregate Object

The Maximum2 Aggregate Object is an instance of AggregateFunctionType and represents the maximum 2 aggregate function defined in 5.4.3.16. See Table 18 for details.

Table 18 – Maximum2 Aggregate Object

Attribute	Value
BrowseName	Maximum2
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - Maximum2

4.2.2.16 MinimumActualTime2 Aggregate Object

The MinimumActualTime2 Aggregate Object is an instance of AggregateFunctionType and represents the minimum actual time 2 aggregate function defined in 5.4.3.17. See Table 19 for details.

Table 19 – MinimumActualTime2 Aggregate Object

Attribute	Value
BrowseName	MinimumActualTime2
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - MinimumActualTime2

4.2.2.17 MaximumActualTime2 Aggregate Object

The MaximumActualTime2 Aggregate Object is an instance of AggregateFunctionType and represents the maximum actual time 2 aggregate function defined in 5.4.3.18. See Table 20 for details.

Table 20 – MaximumActualTime2 Aggregate Object

Attribute	Value
BrowseName	MaximumActualTime2
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - MaximumActualTime2

4.2.2.18 Range2 Aggregate Object

The Range2 Aggregate Object is an instance of AggregateFunctionType and represents the range 2 aggregate function defined in 5.4.3.19. See Table 21 for details.

Table 21 – Range2 Aggregate Object

Attribute	Value
BrowseName	Range2
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - Range2

4.2.2.19 Count Aggregate Object

The Count Aggregate Object is an instance of AggregateFunctionType and represents the count aggregate function defined in 5.4.3.21. See Table 22 for details.

Table 22 – Count Aggregate Object

Attribute	Value
BrowseName	Count
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - Count

4.2.2.20 DurationInStateZero Aggregate Object

The DurationInStateZero Aggregate Object is an instance of AggregateFunctionType and represents the duration in state zero aggregate function defined in 5.4.3.22. See Table 23 for details.

Table 23 – DurationInStateZero Aggregate Object

Attribute	Value
BrowseName	DurationInStateZero
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - DurationInStateZero

4.2.2.21 DurationInStateNonZero Aggregate Object

The DurationInStateNonZero Aggregate Object is an instance of AggregateFunctionType and represents the duration in state non-zero aggregate function defined in 5.4.3.23. See Table 24 for details.

Table 24 – DurationInStateNonZero Aggregate Object

Attribute	Value
BrowseName	DurationInStateNonZero
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - DurationInStateNonZero

4.2.2.22 NumberOfTransitions Aggregate Object

The NumberOfTransitions Aggregate Object is an instance of AggregateFunctionType and represents the number of transitions aggregate function defined in 5.4.3.24. See Table 25 for details.

Table 25 – NumberOfTransitions Aggregate Object

Attribute	Value
BrowseName	NumberOfTransitions
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - NumberOfTransitions

4.2.2.23 Start Aggregate Object

The Start Aggregate Object is an instance of AggregateFunctionType and represents the start aggregate function defined in 5.4.3.25. See Table 26 for details.

Table 26 – Start Aggregate Object

Attribute	Value
BrowseName	Start
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - Start

4.2.2.24 End Aggregate Object

The End Aggregate Object is an instance of AggregateFunctionType and represents the end aggregate function defined in 5.4.3.26. See Table 27 for details.

Table 27 – End Aggregate Object

Attribute	Value
BrowseName	End
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - End

4.2.2.25 Delta Aggregate Object

The Delta Aggregate Object is an instance of AggregateFunctionType and represents the delta aggregate function defined in 5.4.3.27. See Table 28 for details.

Table 28 – Delta Aggregate Object

Attribute	Value
BrowseName	Delta
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - Delta

4.2.2.26 StartBound Aggregate Object

The StartBound Aggregate Object is an instance of AggregateFunctionType and represents the start bound aggregate function defined in 5.4.3.28. See Table 29 for details.

Table 29 – StartBound Aggregate Object

Attribute	Value
BrowseName	StartBound
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - StartBound

4.2.2.27 EndBound Aggregate Object

The EndBound Aggregate Object is an instance of AggregateFunctionType and represents the end bound aggregate function defined in 5.4.3.29. See Table 30 for details.

Table 30 – EndBound Aggregate Object

Attribute	Value
BrowseName	EndBound
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - EndBound

4.2.2.28 DeltaBounds Aggregate Object

The DeltaBounds Aggregate Object is an instance of AggregateFunctionType and represents the delta bounds aggregate function defined in 5.4.3.30. See Table 31 for details.

Table 31 – DeltaBounds Aggregate Object

Attribute	Value
BrowseName	DeltaBounds
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - DeltaBounds

4.2.2.29 DurationGood Aggregate Object

The DurationGood Aggregate Object is an instance of AggregateFunctionType and represents the duration good aggregate function defined in 5.4.3.31. See Table 32 for details.

Table 32 – DurationGood Aggregate Object

Attribute	Value
BrowseName	DurationGood
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - DurationGood

4.2.2.30 DurationBad Aggregate Object

The DurationBad Aggregate Object is an instance of AggregateFunctionType and represents the duration bad aggregate function defined in 5.4.3.32. See Table 33 for details.

Table 33 – DurationBad Aggregate Object

Attribute	Value
BrowseName	DurationBad
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - DurationBad

4.2.2.31 PercentGood Aggregate Object

The PercentGood Aggregate Object is an instance of AggregateFunctionType and represents the percent good aggregate function defined in 5.4.3.33. See Table 34 for details.

Table 34 – PercentGood Aggregate Object

Attribute	Value
BrowseName	PercentGood
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - PercentGood

4.2.2.32 PercentBad Aggregate Object

The PercentBad Aggregate Object is an instance of AggregateFunctionType and represents the percent bad aggregate function defined in 5.4.3.34. See Table 35 for details.

Table 35 – PercentBad Aggregate Object

Attribute	Value
BrowseName	PercentBad
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - PercentBad

4.2.2.33 WorstQuality Aggregate Object

The WorstQuality Aggregate Object is an instance of AggregateFunctionType and represents the worst quality aggregate function defined in 5.4.3.35. See Table 36 for details.

Table 36 – WorstQuality Aggregate Object

Attribute	Value
BrowseName	WorstQuality
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - WorstQuality

4.2.2.34 WorstQuality2 Aggregate Object

The WorstQuality2 Aggregate Object is an instance of AggregateFunctionType and represents the worst quality 2 aggregate function defined in 5.4.3.36. See Table 37 for details.

Table 37 – WorstQuality2 Aggregate Object

Attribute	Value
BrowseName	WorstQuality2
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - WorstQuality2

4.2.2.35 AnnotationCount Aggregate Object

The AnnotationCount Aggregate Object is an instance of AggregateFunctionType and represents the annotation count aggregate function defined in 5.4.3.20. See Table 38 for details.

Table 38 – AnnotationCount Aggregate Object

Attribute	Value
BrowseName	AnnotationCount
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - AnnotationCount

4.2.2.36 StandardDeviationSample Aggregate Object

The StandardDeviationSample Aggregate Object is an instance of AggregateFunctionType and represents the standard deviation sample aggregate function defined in 5.4.3.37. See Table 39 for details.

Table 39 – StandardDeviationSample Aggregate Object

Attribute	Value
BrowseName	StandardDeviationSample
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - StandardDeviationSample

4.2.2.37 VarianceSample Aggregate Object

The VarianceSample Aggregate Object is an instance of AggregateFunctionType and represents the variance sample aggregate function defined in 5.4.3.38. See Table 40 for details.

Table 40 – VarianceSample Aggregate Object

Attribute	Value
BrowseName	VarianceSample
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - VarianceSample

4.2.2.38 StandardDeviationPopulation Aggregate Object

The StandardDeviationPopulation Aggregate Object is an instance of AggregateFunctionType and represents the standard deviation population aggregate function defined in 5.4.3.39. See Table 41 for details.

Table 41 – StandardDeviationPopulation Aggregate Object

Attribute	Value
BrowseName	StandardDeviationPopulation
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - StandardDeviationPopulation

4.2.2.39 VariancePopulation Aggregate Object

The VariancePopulation Aggregate Object is an instance of AggregateFunctionType and represents the variance population aggregate function defined in 5.4.3.40. See Table 42 for details.

Table 42 – VariancePopulation Aggregate Object

Attribute	Value
BrowseName	VariancePopulation
References		Node Class	BrowseName	DataType	TypeDefinition	ModellingRule
HasTypeDefinition		Object Type	AggregateFunctionType
Conformance Units
Aggregates - VariancePopulation

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 OPC 10000-4.

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.

Figure 1 – Representation of Aggregate Configuration information in the AddressSpace