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 may have the same BrowseName. They are used to build a browse path between two Nodes or to define a standard Property.
Servers may often choose to use the same namespace for the NodeId and the BrowseName. However, if they want to provide a standard Property, its BrowseName shall have the namespace of the standards body although the 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.
Table 38 provides a list of namespaces and their index used for BrowseNames in this document. The default namespace of this document is not listed since all BrowseNames without prefix use this default namespace.
Table 38 – Namespaces used in this document
|
NamespaceURI |
Namespace Index |
Example |
|
0 |
0:EngineeringUnits |
|
|
2 |
2:Registrar |
|
|
3 |
3:ApplicationRecordDataType |