Part 17: Alias Names
| Document number | OPC 10000-17 |
|---|---|
| IEC designation | IEC 62541-17 |
| Colloquially | Part 17 |
| Group | Utility |
Part 17 defines a way to reach nodes by an external name - a plant designation, a KKS code, a legacy tag - instead of by browse path. A server publishes categories of alias names, each mapping one name to one or more nodes, and offers a method to resolve them.
What problem it solves
Every plant already has a naming system, and it is never the OPC UA browse path. Instrument tags, plant designation codes and the tag names inherited from a previous control system are what the drawings, the maintenance system and the operators use. Part 17 lets a server publish those names as a first-class lookup surface, so a client can ask for the node behind a designation without anyone maintaining a mapping spreadsheet on the side.
How it is modelled
Alias names live in a hierarchy of category objects beneath a standard AliasNames folder, which lets a server separate several naming systems - one category for plant designations, another for legacy tags - rather than flattening them into one namespace. Each alias name node references the nodes it designates, and the reference carries which kind of relationship it is, so one alias can point at a value, its alarm condition and its history in a structured way. A resolution method takes a name and returns the matching entries.
Adoption, honestly
There is a server capability code, ALIAS, that a server can advertise so a discovery client knows the feature is there. In the field it is uncommon. The mechanism is well designed and solves a real problem, and most servers simply do not implement it, which means an integration that depends on alias resolution has to be confirmed against the specific server and version in front of you rather than specified in the abstract.
What it defines
| Concept | What it is |
|---|---|
| AliasNames folder | The standard entry point in the address space under which alias categories are published. Browse here to find out whether a server implements the feature at all. |
| Alias name category | A container grouping aliases from one naming system, nestable, so plant designations and legacy tags stay separate and separately discoverable. |
| Alias name node | One external name, referencing the nodes it designates. The reference type on each link says what role that node plays for the alias. |
| One-to-many mapping | An alias may designate several nodes - a value, its condition, its history. Resolution therefore returns a list, and picking the first entry is a guess. |
| Resolution method | A method that takes an alias name and returns the matching references, so a client resolves at runtime rather than caching a mapping that goes stale. |
| ALIAS capability code | The server capability string advertising alias-name support, filterable through network discovery before a client connects. |
| Relation to dictionary references | Alias names give an alternative address for a node; dictionary references give it external semantics. Different problems, and a model can use both. |
Do you need to read it?
Integrators bridging an OPC UA server to a system that thinks in plant designations - a maintenance system, a historian with an inherited tag list, or an operator-facing tool. It is also worth knowing about when specifying a new server, because asking for alias-name support up front is far cheaper than building the mapping layer yourself later.
Traps that trace back to this part
- Adoption is thin. Treat alias-name support as a feature to verify on the actual server and firmware version, not as something to assume from a standard that defines it. Browse for the AliasNames folder during evaluation.
- Resolution returns a set, not a node. An alias legitimately designates a value node, its alarm condition and its historical configuration, so client code that takes the first match will sometimes subscribe to the wrong thing. Inspect the reference type on each result.
- Alias names are a plant-designation overlay maintained by whoever owns the tag list, so they can be renamed without any change to the underlying model. Keep the resolved NodeId and namespace URI as the durable identity and re-resolve the alias rather than storing it as the primary key.
Last verified 7 September 2026 against OPC UA 1.05.07. The specification parts themselves are published by the OPC Foundation. OPC UA Connect is an educational resource and is not affiliated with the OPC Foundation.