The HistoryRead service defined in OPC 10000-4 can perform several different functions. The historyReadDetails parameter is an Extensible Parameter that specifies which function to perform. The ReadProcessedDetails structure is used to read aggregated data for HistoricalDataNodes.
The CreateMonitoredItems Service allows specifying a filter for each MonitoredItem. The MonitoringFilter is an extensible parameter whose structure depends on the type of item being monitored. The AggregateFilter structure is used to obtain aggregated data for a subscription.
ReadProcessedDetails structure is formally detailed in OPC 10000-11. Table 6 outlines the components of the ReadProcessedDetails structure for the purposes of discussion in this document.
Table 6 – ReadProcessedDetails
|
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 Aggregate values. |
|
aggregateType[] |
The NodeIds of the AggregateFunction Objects. AggregateFunction Objects indicate the list of Aggregates to be used when retrieving processed history. |
|
aggregateConfiguration |
Aggregate configuration 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 AggregateFilter defines the Aggregate function that should be used to calculate the values to be returned. The AggregateFilte r is formally defined in OPC 10000-4. Table 7 outlines the components of the AggregateFilter structure for the purposes of discussion in this document.
Table 7 – AggregateFilter structure
|
Name |
Description |
|
AggregateFilter |
|
|
startTime |
Beginning of period to calculate the Aggregate the first time. |
|
aggregateType |
The NodeIds of the AggregateFunction Objects that indicates the list of Aggregates to be used when retrieving processed data. |
|
processingInterval |
The period to be used to compute the Aggregate. |
|
aggregateConfiguration |
This parameter allows Clients to override the Aggregate configuration settings supplied by an AggregateConfiguration Object on 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. |