7.2.5.5.2 DataSetMetaData
DataSetMetaData describe the content of DataSetMessages published by a DataSetWriter. More specifically, it specifies the names and data types of the values that shall appear in the Payload of a DataSetMessage.
When the DataSetMetaData of a DataSet changes, the DataSetWriter may be configured to publish the updated value through the mechanism defined by the transport protocol mapping.
The DataSetWriterId and Version fields in a DataSetMessage are used to correlate a DataSetMessage with a DataSetMetaData.
A NetworkMessage with MessageType DataSetMetaData is a JSON object with the fields defined in Table 188.
| Name | Type | Description |
| MessageId | String | A globally unique identifier for the message. This value is mandatory. |
| MessageType | String | This value shall be “ua-metadata”. This value is mandatory. |
| PublisherId | String | A unique identifier for the Publisher. It identifies the source of the message. This value is mandatory. |
| DataSetWriterId | UInt16 | An identifier for DataSetWriter which published the DataSetMetaData. This value is mandatory. It is unique within the scope of a Publisher. |
| WriterGroupName | String | The name of the WriterGroup which created the NetworkMessage. This value is mandatory. |
| DataSetWriterName | String | The name of the DataSetWriter. This value is mandatory. |
| Timestamp | UtcTime | When the message was first sent to the middleware. This value is mandatory. |
| MetaData | DataSetMetaDataType | The metadata as defined in 6.2.3.2.3. This value is mandatory. |
All fields are encoded using CompactEncoding OPC UA JSON Data Encoding defined in OPC 10000-6 .