8 Standard DataTypes ToC Previous Next

8.2 NodeId ToC Previous Next

8.2.4 Identifier value ToC Previous Next

The Identifier value element is used within the context of the first three elements to identify the Node. Its data type and format is defined by the IdType.

Identifier values of IdType String are restricted to 4096 characters. Identifier values of IdType Opaque are restricted to 4096 bytes.

A Node in the AddressSpace shall not have a null NodeId. However, many services defined in OPC 10000-4 define special behaviour if a null NodeId is passed as a parameter.

A canonical null NodeId has an IdType equal to Numeric, a NamespaceIndex equal to 0 and an Identifier equal to 0.

In addition to the canonical null NodeId the alternative values defined in Table 23 shall be considered a null NodeId.

Table 23 – NodeId Alternative Null Values

IdType NamespaceIndex Null Value
String 0 A null or Empty String (“”)
Guid 0 A Guid initialised with zeros (e.g. 00000000-0000-0000-0000-000000)
Opaque 0 A null or Empty ByteString

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