This Built-in DataTypeis used to define XML elements. OPC 10000-6defines details about this DataType.

XML data can always be modelled as a subtype of the Structure DataTypewith a single DataTypeEncodingthat represents the XML complexType that defines the XML element (it is not necessary to have access to the XML Schema to define a DataTypeEncoding). For this reason a Servershould never define Variablesthat use the XmlElement DataTypeunless the Serverhas no information about the XML elements that might be in the Variable Value.