DataSetMetaDatadescribes the content and semantic of a DataSet. The structure description includes overall DataSetattributes (e.g. name and version) and a set of fields with their name and data type. The order of the fields in the DataSetMetaDatashall match the order of values in the published DataSetMessages.

The DataSetMetaDataTypeis defined in 6.2.2.1.2.

Example description (simplified, in pseudo-language):

Name: “Temperature-Sensor Measurement”

Fields: [1] Name=DeviceName, Type=String

[2] Name=Temperature, Type=Float, Unit=Celsius, Range={1,100}

Subscribersuse the DataSetMetaDatafor decoding the values of a DataSetMessageto a DataSet.Subscribersmay use name and data type for further processing or display of the published data.

Each DataSetMessagealso includes the version of the DataSetMetaDatathat it complies with. This allows Subscribersto verify if they have the corresponding DataSetMetaData. The related ConfigurationVersionDataTypeis defined in 6.2.2.1.5.

DataSetMetaDatamay be specific to a single PublishedDataSet or identical for all PublishedDataSetsthat are configured based on a DataSetClass(see 5.2.2).

There are multiple options for Subscribersto get the initial DataSetMetaData:

• The Subscriberis an OPC UA Clientand is able to get the necessary configuration information from the PubSubconfiguration model (see 9.1.4.2.1) provided by the Publisher, from a configuration server or from a directory server.
• The Subscribersupports the OPC UA configuration Methodsdefined in the PubSubconfiguration model.
• The Subscriberreceives the DataSetMetaDataas NetworkMessagefrom the Publisher. This may require an option for the Subscriberto request this NetworkMessagefrom the Publisher.
• The Subscriberis configured with product specific configuration means.

There are multiple options to exchange the DataSetMetaDatabetween Publisherand Subscriberif the configuration changes.

• The DataSetMetaDatais sent as a NetworkMessagefrom the Publisherto the Subscriberbefore DataSetMessageswith changed content are sent. The used Message Oriented Middlewareshould ensure reliable delivery of the message. The mapping for the Message Oriented Middlewaredefines a way for the Subscriberto request the DataSetMetaData. The Subscribergoes to an error state if it has not received the new DataSetMetaDatathat matches the ConfigurationVersion of the received DataSetMessage.
• The Subscriberis automatically updated via the OPC UA configuration Methodsdefined in the PubSubconfiguration model when the DataSetin the Publisheris updated.
• The Subscriberis an OPC UA Clientand is able to obtain the update from the Publisheror a configuration server via the information exposed by the PubSubconfiguration model.
• The Subscriberis updated with product specific configuration means when the DataSetin thePublisheris changed.