UA Part 13: Aggregates - 4.2 Aggregate Objects

OPC UA Serverscan support several different functionalities and capabilities.The following standard Objectsare 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 Nodethat defines the Aggregateconfiguration of any Variableor Property.AggregateConfiguration Objectrepresents the browse entry point for information on how the Servertreats Aggregatespecific 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 BaseObjectTypedefined 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 Variableindicates how the Servertreats data returned with a StatusCodeseverity Uncertain with respect to Aggregatecalculations.A value of True indicates the Serverconsiders the severity equivalent to Bad, a value of False indicates the Serverconsiders the severity equivalent to Good, unless the Aggregatedefinition says otherwise. The default value is True. Note that the value is still treated as Uncertain when the StatusCodefor the result is calculated.

The PercentDataBad Variableindicates the minimum percentage of Bad data in a given interval required for the StatusCode for the given interval for processed data requestto be set to Bad. (Uncertain is treated as defined above.)Refer to 5.4.3for details on using this Variablewhen assigning StatusCodes. For details on which Aggregatesuse the PercentDataBad Variable, see the definition of each Aggregate. The default value is 100.

The PercentDataGood Variableindicates the minimum percentage of Gooddata in a given interval required for the StatusCode for the given interval for the processed data requeststo be set to Good. Refer to 5.4.3for details on using this Variablewhen assigning StatusCodes. For details on which Aggregatesuse the PercentDataGood Variable, see the definition of each Aggregate. The default value is 100.

The following calculations are used to detemine the StatusCodewhich will be used to calculate the value of the aggregate. Refer to 5.4.3 for details on using these Variableswhen assigning StatusCodes. The PercentDataGoodand PercentDataBadshall follow the following relationship PercentDataGood≥ (100 – PercentDataBad). If they are equal the result of the PercentDataGood calculation is used. If the values entered for PercentDataGoodand PercentDataBaddo 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 PercentDataGoodor PercentDataBad exceed 100.

The UseSlopedExtrapolation Variableindicates how the Serverinterpolates data when no boundary value exists (i.e. extrapolating into the future from the last known value).A value of False indicates that the Serverwill use a SteppedExtrapolationformat, and hold the last known value constant.A value of True indicates the Serverwill project the value using UseSlopedExtrapolationmode.The default value is False.For SimpleBounds this value is ignored.

4.2.2 AggregateFunction Object

4.2.2.1 General

This Objectis used as the browse entry point for information about the Aggregates supported by a Server. The content of this Objectis already defined by its type definition. All Instancesof the FolderTypeuse the standard BrowseNameof ‘AggregateFunctions’. The HasComponent Referenceis used to relate a ServerCapabilities Objectand/or any HistoryServerCapabilitiesType Objectto 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 ServerCapabilitiesand HistoryServerCapabilitiesType Objectshall reference an AggregateFunction Object. In addition, each HistoricalConfiguration Objectbelonging to a HistoricalDataNodemay reference an AggregateFunction Objectusing the HasComponent Reference.

4.2.2.2 AggregateFunctionType

This ObjectTypedefines an Aggregatesupported by a UA Server. This Objectis 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 BaseObjectTypedefined in OPC 10000-5
Conformance Units
Historical Access Aggregates

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

Table 5specifies the BrowseNameand Description Attributesfor 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
	Interpolation Aggregate
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 StatusCodeof data in the interval.
WorstQuality2	Retrieve the worst StatusCodeof data in the interval including the Simple Bounding Values.
AnnotationCount	Retrieve the number of Annotations in the interval (applies to Historical Aggregatesonly).
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.
StandardDeviation Population	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.