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

BrowseName

HistoricalDataConfigurationType

IsAbstract

False

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.