The HistoryRead Servicedefined in OPC 10000-4can perform several different functions. The HistoryReadDetailsparameter is an Extensible Parameterthat specifies which function to perform and the details that are specific to that function. See OPC 10000-4for the definition of Extensible Parameter. Table 19lists the symbolic names of the valid Extensible Parameterstructures. Some structures will perform different functions based on the setting of its associated parameters. For simplicity a functionality of each structure is listed. For example, text such as ‘using the Read modified functionality’ refers to the function the HistoryRead Serviceperforms using the Extensible Parameterstructure ReadRawModifiedDetails with the isReadModified Boolean parameter set to TRUE.

Table 19– HistoryReadDetails parameterTypeIds

Symbolic Name

Functionality

Description

ReadEventDetails

Read event

This structure selects a set of Eventsfrom the history database by specifying a filter and a time domain for one or more Objects orViews. See 6.4.2.1.

When this parameter is specified the Serverreturns a HistoryEvent structure for each operation (see 6.5.4).

ReadRawModifiedDetails

Read raw

This structure selects a set of values from the history database by specifying a time domain for one or more Variables. See 6.4.3.1.

When this parameter is specified the Serverreturns a HistoryData structure for each operation (see 6.5.2).

ReadRawModifiedDetails

Read modified

This parameter selects a set of modified valuesfrom the history database by specifying a time domain for one or more Variables. See 6.4.3.1.

When this parameter is specified the Serverreturns a HistoryModifiedData structure for each operation (see 6.5.3).

ReadProcessedDetails

Read processed

This structure selects a set of Aggregatevalues from the history database by specifying a time domain for one or more Variables. See 6.4.4.1.

When this parameter is specified the Serverreturns a HistoryData structure for each operation (see 6.5.2)

ReadAtTimeDetails

Read at time

This structure selects a set of raw or interpolated values from the history database by specifying a series of timestamps for one or more Variables. See 6.4.5.1.

When this parameter is specified the Serverreturns a HistoryData structure for each operation (see Clause 6.5.2).

ReadAnnotationDataDetails

Read Annotation Data

This structure selects a set of Annotation Datafrom the history database by specifying a series of timestamps for one or more Variables. See 6.4.6.1.

When this parameter is specified the Serverreturns a HistoryAnnotationData structure for each operation (see Clause 6.5.5).