What is the complete format of an OPC UA NodeId?
D — All of the above are valid
A NodeId is a tuple (Namespace Index, Identifier) and the standard defines four identifier types, so all the partial answers are correct: i= for a 32-bit numeric identifier (the most network-efficient), s= for a string identifier (human-readable, e.g. "Pump1.Status"), g= for a 128-bit GUID, and b= for an opaque byte string. Option A is incomplete because it only covers the numeric form. Option B is incomplete because it only covers the string form. Option C is incomplete because it only covers the GUID form. The URI form looks like ns=2;s=Boiler1.Temperature, where namespace index 0 is the OPC UA Foundation, 1 is the local server, and 2+ are vendor or Companion Spec namespaces.
Never hard-code a numeric NodeId across firmware versions: numeric identifiers are vendor-allocated and can shift, whereas string NodeIds are usually stable and self-documenting.
- A.ns=N;i=Identifier (numeric)
- B.ns=N;s=Identifier (string)
- C.ns=N;g=Identifier (GUID)
- D.All of the above are valid✓
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