OPC UA uses namespaces 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 defined outside of this document shall not use the standard namespaces defined in this document.
Table 236 provides a list of mandatory and optional namespaces used in a Server supporting OPC UA FX.
Table 236 – Namespaces used in a UAFX Server
|
NamespaceURI |
Description |
Use |
|
Namespace for NodeIds and BrowseNames defined in the OPC UA specification. This namespace shall have the namespace index 0. |
Mandatory |
|
|
Local Server URI |
Namespace for nodes defined in the local server. This may include types and instances used in an OPC UA FX application represented by the Server. This namespace shall have namespace index 1. |
Mandatory |
|
Namespace for common DataType that are shared between a ConnectionManager and an AutomationComponent. |
Mandatory |
|
|
Namespace for NodeIds and BrowseNames defined in the AutomationComponent related part of this document. The namespace index is Server-specific. A Server shall support either the AutomationComponent or the ConnectionManager to be considered an OPC UA FX Server. |
Optional |
|
|
Namespace for NodeIds and BrowseNames defined in the ConnectionManager-related part of this document. The namespace index is Server-specific. A Server shall support either the AutomationComponent or the ConnectionManager to be considered an OPC UA FX Server. |
Optional |
|
|
Namespace for NodeIds and BrowseNames defined in OPC UA Part 100. The namespace index is Server-specific. |
Mandatory |
|
|
Vendor-specific types |
A Server may 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 |
Table 237 provides a list of namespaces and their index used for BrowseNames in this document. The NamespaceIndexes stated here are used as abbreviations throughout this document. Since NamespaceIndexes are dynamically assigned during the start of a Server, the NamespaceIndex, for example, for DI, may be different from 5 in a specific Server.
Table 237 – Namespaces used in this Document
|
NamespaceURI |
Namespace Index |
Example |
|
0 |
0:EngineeringUnits |
|
|
2 |
2:FxCommandMask |
|
|
3 |
3:AutomationComponentType |
|
|
4 |
4:ConnectionManagerType |
|
|
5 |
5:DeviceRevision |