A DataSetMessage is produced by a DataSetWriter and contains list of name/value pairs which are specified by the PublishedDataSet associated with the DataSetWriter. The contents of the DataSetMessage are formally described by a DataSetMetData Objects. A DataSetMessage is a JSON object with the fields defined in Table 92.

DataSetWriters may periodically provide keep-alive messages which are DataSetMessages without any Payload field.

Table 92 – JSON DataSetMessage Definition

Name

Type

Description

DataSetWriterId

String

An identifier for DataSetWriter which created the DataSetMessage.

This value is mandatory.

It is unique within the scope of a Publisher.

SequenceNumber

UInt32

A strictly monotonically increasing sequence number assigned to the DataSetMessage by the DataSetWriter.

This value is optional. The presence of the value depends on the setting in the JsonDataSetMessageContentMask.

MetaDataVersion

ConfigurationVersionDataType

The version of the DataSetMetaData which describes the contents of the Payload.

This value is optional. The presence of the value depends on the setting in the JsonDataSetMessageContentMask.

Timestamp

DateTime

A timestamp which applies to all values contained in the DataSetMessage.

This value is optional. The presence of the value depends on the setting in the JsonDataSetMessageContentMask.

Status

StatusCode

A status code which applies to all values contained in the DataSetMessage.

This value is optional. The presence of the value depends on the setting in the JsonDataSetMessageContentMask.

Payload

Object

A JSON object containing the name-value pairs specified by the PublishedDataSet.

The format of the value depends on the DataType of the field and the flags specified by the DataSetMessageContentMask.

All fields with a concrete DataType are encoded using reversible OPC UA JSON Data Encoding defined in OPC 10000-6.

The fields in the DataSetMessage are specified by the DataSetFieldContentMask in the DataSetWriter parameters.

DataSetFieldContentMask specifies the format of the field values in the Payload according to the following rules: