## 5.2.2 HistoricalDataConfigurationType

The Historical Access Data model extends the standard type model by defining the HistoricalDataConfigurationType. This Object defines the general characteristics of a Node that defines the historical configuration of any HistoricalDataNode that is defined to contain history. It is formally defined in Table 3.

All Instances of the HistoricalDataConfigurationType use the standard BrowseName as 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 Object represents the browse entry point for information on how the Server treats Aggregate specific functionality such as handling Uncertain data. This Object is required to be present even if it contains no Aggregate configuration Objects. Aggregates are defined inOPC 10000-13.

AggregateFunctions is an entry point to browse to all Aggregate capabilities supported by the Server for Historical Access. All HistoryAggregates supported by the Server should be able to be browsed starting from this Object. Aggregates are defined inOPC 10000-13.

The Stepped Variable specifies 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 data is examined. This Property also effects how some Aggregates are calculated. A value of True indicates the stepped interpolation mode. A value of False indicates SlopedInterpolation mode. The default value is False.

The Definition Variable is a vendor-specific, human readable string that specifies how the value of this HistoricalDataNode is 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 Variable specifies the maximum interval between data points in the history repository regardless of their value change (see OPC 10000-3 for definition of Duration).

The MinTimeInterval Variable specifies the minimum interval between data points in the history repository regardless of their value change (see OPC 10000-3 for definition of Duration).

The ExceptionDeviation Variable specifies the minimum amount that the data for the HistoricalDataNode shall change in order for the change to be reported to the history database.

The ExceptionDeviationFormat Variable specifies how the ExceptionDeviation is determined. Its values are defined in Table 4.

The StartOfArchive Variable specifies the date before which there is no data in the archive either online or offline.

The StartOfOnlineArchive Variable specifies the date of the earliest data in the online archive.

The ServerTimestampSupported Variable indicates support for the ServerTimestamp capability. A value of True indicates the Server supports ServerTimestamps in 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.