This Built-in DataType is composed of three elements that identify a Node within a Server. They are defined in Table 21.
| Name | Type | Description | 
| NodeId | structure | 
 | 
| NamespaceIndex | UInt16 | The index for a namespace URI (see 8.2.2). | 
| IdType | Enum | The format and data type of the identifier (see 8.2.3). | 
| Identifier | * | The identifier for a Node in the AddressSpace of an OPC UA Server (see 8.2.4). | 
See OPC 10000-6 for a description of the encoding of the identifier into OPC UA Messages.