The HistoryReadservice defined in OPC 10000-4can perform several different functions. The historyReadDetailsparameter is an Extensible Parameterthat specifies which function to perform.The ReadProcessedDetailsstructure is used to read aggregated data for HistoricalDataNodes.
The CreateMonitoredItems Serviceallows specifying a filter for each MonitoredItem. The MonitoringFilteris an extensible parameter whose structure depends on the type of item being monitored. The AggregateFilterstructure is used to obtain aggregated data for a subscription.
ReadProcessedDetails structure is formally detailed in OPC 10000-11. Table 6outlines the components of the ReadProcessedDetails structure for the purposes of discussion in this document.
|
Name |
Description |
|
ReadProcessedDetails |
Specifies the details used to perform a “processed” history read. |
|
startTime |
Beginning of period to read. |
|
endTime |
End of period to read. |
|
processingInterval |
Interval between returned Aggregatevalues. |
|
aggregateType[] |
The NodeIdsof the AggregateFunction Objects. AggregateFunction Objectsindicate the list of Aggregates to be used when retrieving processed history. |
|
aggregateConfiguration |
Aggregateconfiguration structure. |
|
useServerDefaults |
If True the Server’s default values are used and any values specified for the other parameters are ignored. |
|
treatUncertainAsBad |
See 4.2.1.2. |
|
percentDataBad |
See 4.2.1.2. |
|
percentDataGood |
See 4.2.1.2. |
|
useSlopedExtrapolation |
See 4.2.1.2. |
The AggregateFilterdefines the Aggregatefunction that should be used to calculate the values to be returned.The AggregateFilter is formally defined in OPC 10000-4. Table 7outlines the components of the AggregateFilterstructure for the purposes of discussion in this document.
Table 7– AggregateFilter structure
|
Name |
Description |
|
AggregateFilter |
|
|
startTime |
Beginning of period to calculate the Aggregatethe first time. |
|
aggregateType |
The NodeIdsof the AggregateFunction Objectsthat indicates the list of Aggregatesto be used when retrieving processed data. |
|
processingInterval |
The period to be used to compute the Aggregate. |
|
aggregateConfiguration |
This parameter allows Clientsto override the Aggregateconfiguration settings supplied by an AggregateConfiguration Objecton a per monitored item basis. |
|
useServerDefaults |
If True the Server’s default values are used and any values specified for the other parameters are ignored. |
|
treatUncertainAsBad |
See 4.2.1.2. |
|
percentDataBad |
See 4.2.1.2. |
|
percentDataGood |
See 4.2.1.2. |
|
useSlopedExtrapolation |
See 4.2.1.2. |