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 specification shall not use the standard namespaces.

Table 109provides a list of mandatory and optional namespaces used in a PROFINET OPC UA Server.

Table 109– Namespaces used in a PROFINET OPC UA Server

NamespaceURI

Description

Use

http://opcfoundation.org/UA/

Namespace for NodeIds and BrowseNames defined 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 may include types and instances used in an PROFINET Device represented by the Server. This namespace shall have namespace index 1.

Mandatory

http://opcfoundation.org/UA/PROFINET/

Namespace for NodeIds and BrowseNames of the base information model defined in this specification. 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 specification 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 110 – Namespaces used in this specificationprovides 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 110– Namespaces used in this specification

NamespaceURI

Namespace Index

Example

http://opcfoundation.org/UA/

0

0:EngineeringUnits