The namespace is a URI that identifies the naming authority responsible for assigning the identifier element of the NodeId. Naming authorities include the local Server, the underlying system, standards bodies and consortia. It is expected that most Nodeswill use the URI of the Serveror of the underlying system.

Using a namespace URI allows multiple OPC UA Serversattached to the same underlying system to use the same identifier to identify the same Object. This enables Clientsthat connect to those Serversto recognise Objectsthat they have in common.

Namespace URIs, like Servernames, are identified by numeric values in OPC UA Servicesto permit more efficient transfer and processing (e.g. table lookups). The numeric values used to identify namespaces correspond to the index into the NamespaceArray. The NamespaceArrayis a Variablethat is part of the Server Objectin the AddressSpace(see OPC 10000-5for its definition).

The URI for the OPC UA namespace is:

http://opcfoundation.org/UA/”

Its corresponding index in the namespace table is 0.

The namespace URI is case sensitive.