The Historical Access Data model extends the standard type model by defining the HistoricalDataConfigurationType.This Objectdefines the general characteristics of a Node that defines the historical configuration of any HistoricalDataNodethat is defined to contain history. It is formally defined in Table 3.
All Instancesof the HistoricalDataConfigurationTypeuse the standard BrowseNameas defined in Table 6.
Table 3– HistoricalDataConfigurationType definition
|
Attribute |
Value |
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|
BrowseName |
HistoricalDataConfigurationType |
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|
IsAbstract |
False |
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|
References |
NodeClass |
BrowseName |
DataType |
TypeDefinition |
ModellingRule |
|
HasComponent |
Object |
AggregateConfiguration |
-- |
AggregateConfigurationType |
Mandatory |
|
HasComponent |
Object |
AggregateFunctions |
-- |
FolderType |
Optional |
|
HasProperty |
Variable |
Stepped |
Boolean |
PropertyType |
Mandatory |
|
HasProperty |
Variable |
Definition |
String |
PropertyType |
Optional |
|
HasProperty |
Variable |
MaxTimeInterval |
Duration |
PropertyType |
Optional |
|
HasProperty |
Variable |
MinTimeInterval |
Duration |
PropertyType |
Optional |
|
HasProperty |
Variable |
ExceptionDeviation |
Double |
PropertyType |
Optional |
|
HasProperty |
Variable |
ExceptionDeviationFormat |
ExceptionDeviationFormat |
PropertyType |
Optional |
|
HasProperty |
Variable |
StartOfArchive |
UtcTime |
PropertyType |
Optional |
|
HasProperty |
Variable |
StartOfOnlineArchive |
UtcTime |
PropertyType |
Optional |
|
HasProperty |
Variable |
ServerTimestampSupported |
Boolean |
PropertyType |
Optional |
AggregateConfiguration Objectrepresents the browse entry point for information on how the Servertreats Aggregatespecific functionality such as handling Uncertain data. This Objectis required to be present even if it contains no Aggregateconfiguration Objects. Aggregatesare defined inOPC 10000-13.
AggregateFunctions is an entry point to browse to all Aggregatecapabilities supported by the Serverfor Historical Access. All HistoryAggregates supported by the Servershould be able to be browsed starting from this Object. Aggregatesare defined inOPC 10000-13.
TheStepped Variablespecifies whether the historical data was collected in such a manner that it should be displayed as SlopedInterpolation(sloped line between points) or as SteppedInterpolation(vertically-connected horizontal lines between points) when raw datais examined. This Propertyalso effects how some Aggregatesare calculated. A value of True indicates the stepped interpolation mode. A value of False indicates SlopedInterpolationmode. The default value is False.
TheDefinition Variableis a vendor-specific, human readable string that specifies how the value of this HistoricalDataNodeis calculated. Definition is non-localized and will often contain an equation that can be parsed by certain Clients.
Example: Definition::= “(TempA – 25) + TempB”
The MaxTimeInterval Variablespecifies the maximum interval between data points in the history repository regardless of their value change (see OPC 10000-3for definition of Duration).
The MinTimeInterval Variablespecifies the minimum interval between data points in the history repository regardless of their value change (see OPC 10000-3for definition of Duration).
The ExceptionDeviation Variablespecifies the minimum amount that the data for the HistoricalDataNodeshall change in order for the change to be reported to the history database.
The ExceptionDeviationFormat Variablespecifies how the ExceptionDeviation is determined. Its values are defined in Table 4.
The StartOfArchive Variablespecifies the date before which there is no data in the archive either online or offline.
The StartOfOnlineArchive Variablespecifies the date of the earliest data in the online archive.
The ServerTimestampSupported Variableindicates support for the ServerTimestampcapability. A value of True indicates the Serversupports ServerTimestampsin addition to SourceTimestamp. The default is False.
Table 4– ExceptionDeviationFormat Values
|
Value |
Description |
|
ABSOLUTE_VALUE_0 |
ExceptionDeviation is an absolute Value. |
|
PERCENT_OF_VALUE_1 |
ExceptionDeviation is a percentage of Value. |
|
PERCENT_OF_RANGE_2 |
ExceptionDeviation is a percentage of InstrumentRange (see OPC 10000-8). |
|
PERCENT_OF_EU_RANGE_3 |
ExceptionDeviation is a percentage of EURange (see OPC 10000-8). |
|
UNKNOWN_4 |
ExceptionDeviation type is Unknown or not specified. |