| msgId | Optional field that contains the ID, if it was specified, of the message to which this is a response. | 
| dvName | Unique name of the DataView definition specified in the event to which this is a response. | 
| fields | Dictionary of field-name/field-position pairs. A field’s position is its index in the fieldNames sequence that is specified in the associated DataView definition. | 
| extraParams | Optional field that future implementations may use. |