Namespaces are used by OPC UA to create unique identifiers across different naming authorities. The Attributes NodeId and BrowseName are identifiers. A Node in the UA AddressSpace is unambiguously identified using a NodeId. Unlike NodeIds, the BrowseName cannot be used to unambiguously identify a Node. Different Nodes canmay have the same BrowseName. They are used to build a browse path between two Nodes or to define a standard Property.
Servers canmay often choose to use the same N namespace for the NodeId and the BrowseName. However, if they want to provide a standard Property, its BrowseName shall have the N namespace of the standards body although the N namespace of the NodeId reflects something else, for example the EngineeringUnits Property. All NodeIds of Nodes not defined in this document shall not use the standard namespaces.
[RQ12.1] Table 43 provides a list of mandatory and optional Namespaces used in an OPC UA Server according to this document.
Table 43 – Namespaces used in a safety Server
NamespaceURI |
Description |
Use |
Namespace for NodeIds and BrowseNames defined in the OPC UA specification. This Namespace shall have Namespace index 0. |
Mandatory |
|
Local server URI |
Namespace for Nodes defined in the local Server. This can include types and instances used in an AutoID Device represented by the Server. This Namespace shall have Namespace index 1. |
Mandatory |
Namespace for NodeIds and BrowseNames defined in this document. The Namespace index is Server-specific. |
Mandatory |
|
Vendor-specific types |
A Server can provide vendor-specific types like types derived from ObjectTypes defined in this document in a vendor-specific Namespace. |
Optional |
Vendor-specific instances |
A Server provides vendor-specific instances of the standard types or vendor-specific instances of vendor-specific types in a vendor-specific Namespace. It is recommended to separate vendor-specific types and vendor-specific instances into two or more namespaces. |
Mandatory |