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 50provides a list of namespaces typically used in a Scheduler OPC UAServer.

Table 50– Namespaces used in a Scheduler Server

NamespaceURI

Description

http://opcfoundation.org/UA/

Namespace for NodeIdsand BrowseNamesdefined in the OPC UA specification. This namespace shall have namespace index 0.

Local Server URI

Namespace for nodes defined in the local server. This namespace shall have namespace index 1.

http://opcfoundation.org/UA/Scheduler/

Namespace for NodeIdsand BrowseNamesdefined in this document. The namespace index is Serverspecific.

Vendor specific types

A Servermay provide vendor-specific types like types derived from ObjectTypes defined in this document in a vendor-specific namespace.

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.

Table 51provides a list of namespaces and their indices used for BrowseNamesin this document. The default namespace of this document is not listed since all BrowseNameswithout prefix use this default namespace.

Table 51– Namespaces used in this document

NamespaceURI

Namespace Index

Example

http://opcfoundation.org/UA/

0

0:EngineeringUnits