Namespaces are used by OPC UA to create unique identifiers across different naming authorities. The Attributes NodeIdand BrowseNameare identifiers. A Nodein the UA AddressSpaceis unambiguously identified using a NodeId. Unlike NodeIds, the BrowseNamecannot be used to unambiguously identify a Node. Different Nodesmay have the same BrowseName. They are used to build a browse path between two Nodesor to define a standard Property.
Serversmay often choose to use the same namespace for the NodeIdand the BrowseName. However, if they want to provide a standard Property, its BrowseNameshall have the namespace of the standards body although the namespace of the NodeIdreflects something else, for example the EngineeringUnits Property. All NodeIdsof Nodesnot defined in this document shall not use the standard namespaces.
Table 128provides a list of mandatory and optional namespaces used in a Machine Tools OPC UAServer.
Table 128– Namespaces used in a Machine Tools Server
|
NamespaceURI |
Description |
Use |
|
Namespace for NodeIdsand BrowseNamesdefined 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 namespace shall have namespace index 1. |
Mandatory |
|
Namespace for NodeIds and BrowseNames defined in OPC 10000-100. The namespace index is Server specific. |
Mandatory |
|
|
Namespace for NodeIdsand BrowseNamesdefined in OPC 40001-1. The namespace index is Serverspecific. |
Mandatory |
|
|
Namespace for NodeIdsand BrowseNamesdefined in OPC 10000-200. The namespace index is Serverspecific. |
Mandatory |
|
|
Namespace for NodeIdsand BrowseNamesdefined in this document. The namespace index is Serverspecific. |
Mandatory |
|
|
Vendor specific types |
A Servermay provide vendor-specific types like types derived from ObjectTypes defined in this document in a vendor-specific namespace. |
Optional |
|
Vendor specific instances |
A Serverprovides 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 129provides a list of namespaces and their index used for BrowseNamesin this document. The default namespace of this document is not listed since all BrowseNameswithout prefix use this default namespace.
Table 129– Namespaces used in this Document
|
NamespaceURI |
Namespace Index |
Example |
|
0 |
0:EngineeringUnits |
|
|
2 |
2:DeviceRevision |
|
|
3 |
3:YearOfConstruction |
|
|
4 |
4:BasicStacklightType |