Namespaces are used by OPC UA to create unique identifiers across different naming authorities. The NodeIdand BrowseName Attributesare identifiers. A Nodein the UA Address Spaceis 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 nodes not defined in this specification shall not use the standard namespaces.

Table 38provides a list of mandatory and optional namespaces used in an OPC UAServerof a CNC system.

Table 38– Namespaces used in an OPC UA Server of a CNC system

Namespace

Description

Use

http://opcfoundation.org/UA/

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

Mandatory

Local Server URI

Namespace for Nodesdefined in the local Server. This may include types and instances used in a device represented by the Server. This namespace shall have namespace index 1.

Mandatory

http://opcfoundation.org/UA/CNC/

Namespace for NodeIdsand BrowsNamesdefined in this specification. The namespace index is Serverspecific.

Mandatory

Table 39provides a list of namespaces and their index used for BrowseNamesin this specification. The default namespace of this specification is not listed since all BrowseNameswithout prefix use this default namespace.

Table 39– Namespaces used in this specification

Namespace

Namespace Index

Example

http://opcfoundation.org/UA/

0

0:EngineeringUnits