OPC UA Namespace Index and URI: Preserve Stable Meaning Across Sessions

Separate the index from its authority

OPC UA uses a namespace index to refer to a URI in the server’s namespace table. The URI identifies the naming authority behind a node identifier. Primary reference: NamespaceIndex.

A stored numeric index is meaningful within its table context. It is not a self-contained universal naming authority. Keep the identifier type and value as well as the namespace meaning when an integration record must remain reproducible.

A hypothetical table change

Imagine namespace index 2 maps to the fictional URI urn:example:process in one accepted session, while that URI occupies index 3 in a later server context. Copying ns=2 alone would retain the old number without establishing the intended authority in the new table.

Create separate worksheet columns for endpoint/application context, namespace URI, observed index, identifier type and identifier value. Ask how the selected client resolves the current mapping. Do not turn the example into a guarantee that an unchanged URI and identifier preserve every semantic property of a changed device.

Preserve a reproducible node reference

Request the selected server’s namespace and node documentation and the consumer’s persistence behavior. Keep any model version or changed variable meaning visible alongside its reference. A matching display name alone does not close an identifier ambiguity.

This guide provides no live browsing, remapping or configuration instructions and claims no OPC UA nodes on HM machinery. It addresses the naming-authority question. Engineering units, data quality, source time and access permission remain separate fields, even when the node reference itself has been identified correctly.

Customer Questions

Primary References

These references support the technical principles discussed in this guide. The worked examples and review questions are educational.

• Primary reference: NamespaceIndex