The IdType element identifies the type of the NodeId, its format and its scope. Its values are defined in Table 22.

Table 22– IdType Values

Name

Value

Description

Numeric

0

Numeric value

String

1

String value

Guid

2

Globally Unique Identifier

Opaque

3

Namespace specific format

Normally the scope of NodeIdsis the Serverin which they are defined. For certain types of NodeIds, NodeIdscan uniquely identify a Nodewithin a system, or across systems (e.g. GUIDs). System-wide and globally-unique identifiers allow Clientsto track Nodes, such as work orders, as they move between OPC UA Serversas they progress through the system.

Opaque identifiers are identifiers that are free-format byte strings that might or might not be human interpretable.

String identifiers are case sensitive. That is, Clientsshall consider them case sensitive. Serversare allowed to provide alternative NodeIds(see 5.2.2) and using this mechanism severs can handle NodeIdsas case insensitive.