The first decision is to decide at what level types are needed. Typically, each Server will provide one Server Object with a well-known NodeId. The NodeIds of the containing Nodes are also well-known because their symbolic name is specified in this standard and the NodeId is based on the symbolic name in OPC 10000-6. Nevertheless, aggregating Servers may want to expose the Server Objects of the OPC UA Servers they are aggregating in their AddressSpace. Therefore, it is very helpful to have a type definition for the Server Object. The Server Object is an Object, because it groups a set of Variables and Objects containing information about the Server. The ServerType is a complex ObjectType, because the basic structure of the Server Object should be well-defined. However, the Server Object can be extended by adding Variables and Objects in an appropriate structure of the Server Object or its containing Objects.