UA-.NETStandard/docs/RuntimeNodeSets.md

Runtime NodeSets

This guide explains how to import one or more NodeSet2 XML documents into a server's address space at startup, without writing a source-generated or hand-coded NodeManager. Configure the files or streams to load. The server imports them in dependency order and registers the resulting nodes.

Within each imported set, types are registered in inheritance order rather than XML record order. A derived type may precede its supertype in the document; an inheritance cycle is rejected before registration. Imported namespace-zero InputArguments and OutputArguments Properties populate their Method's typed signature, retaining the declared Property NodeIds, argument order, and values.

Contents

• When to use the runtime NodeSet path
• Startup and live lifecycle semantics
  • Shadow reload
  • Immediate reload
• Quick-start examples
  • Single file
  • Single file with a fluent callback
  • Group of dependent NodeSets
  • Custom stream source
  • Direct factory registration
• Stream ownership contract
• Default namespace for unqualified browse paths
• Dependency sorting
  • Referencing a Node another NodeManager owns
• Complex types
• Imported security policy
• Comparison with source-generated NodeManagers
• Related documentation

When to use the runtime NodeSet path

Use AddRuntimeNodeSet when:

• You receive a NodeSet2 XML from a companion-specification vendor and want to host its nodes without regenerating source.
• Your information model changes frequently enough that rebuilding the source-generated manager for every XML update would be disruptive.
• You are prototyping or testing a new NodeSet2 design.

Use the source-generated path when you want compile-time safety, strong typing, and AOT-safe named constants for every node in your model. The runtime path gives you generic NodeState objects and untyped browse-path wiring.

Imported security policy

Runtime import retains node-local RolePermissions and AccessRestrictions. When a node omits either attribute, import applies the corresponding default from its owning Models/Model entry. Ownership follows the node's namespace URI, not its BrowseName, the order of model entries, or the server's namespace index. Defaults are materialized before the nodes enter the address space, so ordinary Read, Write, Call and subscription authorization use the same policy.

An explicit empty node ACL or AccessRestrictions="0" remains an explicit local override; it does not inherit the model setting. An omitted model restriction has the NodeSet schema's default of zero and does not manufacture a node-local restriction. Normal namespace defaults and application permission callbacks still apply. Type-hierarchy visibility exemptions are enforced by the server, not by removing imported policy: metadata remains available for operations that require authorization.

Startup and live lifecycle semantics

AddRuntimeNodeSet on IOpcUaServerBuilder remains the startup path: its factory is created before the server starts and its NodeSet is imported during CreateAddressSpaceAsync. After startup, the resulting generation-1 registration is available from INodeManagerLifecycle.Registrations, so a model composed at startup can use the same reload and removal APIs as one added while the server is already running.

For example, a startup task can locate the registration by an owned model namespace:

public sealed class ModelRegistration(INodeManagerLifecycle lifecycle)
    : IServerStartupTask
{
    public NodeManagerRegistration? Registration { get; private set; }

    public ValueTask OnServerStartedAsync(
        IServerContext server,
        CancellationToken ct)
    {
        Registration = lifecycle.Registrations.Find(registration =>
            registration.NamespaceUris.Contains("urn:example:MyMachine"));
        return default;
    }
}

Running servers also expose INodeManagerLifecycle. Resolve it from dependency injection in a hosted server, or use StandardServer.NodeManagerLifecycle when constructing the server directly. The lifecycle provider can add, reload, shadow-reload, and remove runtime NodeSets without restarting the server.

public sealed class ModelLoader(INodeManagerLifecycle lifecycle)
{
    private NodeManagerRegistration? m_registration;

    public async ValueTask LoadAsync(CancellationToken ct)
    {
        m_registration = await lifecycle.AddRuntimeNodeSetAsync(
            new RuntimeNodeSetOptions
            {
                Sources = [RuntimeNodeSetSource.FromFile("Models/MyMachine.NodeSet2.xml")]
            },
            callerContext: null,
            ct);
    }

    public async ValueTask ReloadAsync(CancellationToken ct)
    {
        m_registration = await lifecycle.ReloadRuntimeNodeSetAsync(
            m_registration!,
            new RuntimeNodeSetOptions
            {
                Sources = [RuntimeNodeSetSource.FromFile("Models/MyMachine.NodeSet2.xml")]
            },
            callerContext: null,
            ct);
    }

    public ValueTask RemoveAsync(CancellationToken ct)
    {
        return lifecycle.RemoveAsync(m_registration!, callerContext: null, ct);
    }
}

Each add returns an immutable NodeManagerRegistration, and reload returns the next generation while invalidating the previous handle.

A registration obtained from Registrations for an AddRuntimeNodeSet model is already the first live generation; pass it directly to ReloadRuntimeNodeSetAsync, ShadowReloadRuntimeNodeSetAsync, ImmediateReloadRuntimeNodeSetAsync, or RemoveAsync.

AddRuntimeNodeSetAsync, ReloadRuntimeNodeSetAsync, and RemoveAsync take the operation the caller is running under. Pass context.GetOperationContext() when calling from a NodeManager or Method callback: a lifecycle operation drains the requests that are in flight, so one started from inside a request would wait for itself and is rejected with an InvalidOperationException. A control-plane caller such as the ModelLoader above is not serving a request and passes null. See Registering NodeManagers.

The rules that apply to every NodeManager registered at runtime -- what happens to MonitoredItems, Browse continuation points, namespace indexes, DataTypes, and change notifications, and which NodeManagers may be reloaded at all -- are described once in Registering NodeManagers. Runtime NodeSets follow those rules, and the built-in runtime NodeSet manager already implements the INodeManagerReloadParticipant contract that reload requires.

Shadow reload

ShadowReloadRuntimeNodeSetAsync permits replacing a generation that still owns active monitored items. Those items stay on the retired generation and continue to be served there until they are deleted or otherwise released; new requests use the replacement generation. Normal reload instead migrates compatible monitored items.

public async ValueTask ShadowReloadAsync(CancellationToken ct)
{
    m_registration = await lifecycle.ShadowReloadRuntimeNodeSetAsync(
        m_registration!,
        new RuntimeNodeSetOptions
        {
            Sources = [RuntimeNodeSetSource.FromFile("Models/MyMachine.NodeSet2.xml")]
        },
        ct);
}

The returned registration replaces the old handle for lifecycle operations. Choose shadow reload only when retaining the old model for existing subscriptions is intentional; its resources remain allocated until those subscriptions drain.

Immediate reload

ImmediateReloadRuntimeNodeSetAsync does not migrate existing monitored items. Affected data-change items receive BadNodeIdUnknown, and clients may recreate items against the replacement model.

The node-manager reload matrix is authoritative for all three modes, including request draining, continuation points, and generation cleanup. Runtime NodeSet reload methods use those same lifecycle operations.

Quick-start examples

Single file

services.AddOpcUa()
    .AddServer(o => { /* … */ })
    .AddRuntimeNodeSet("Models/MyMachine.NodeSet2.xml");

Single file with a fluent callback

Wire read/write/method handlers on top of the imported nodes using the existing untyped INodeManagerBuilder surface:

services.AddOpcUa()
    .AddServer(o => { /* … */ })
    .AddRuntimeNodeSet(
        "Models/MyMachine.NodeSet2.xml",
        nodes =>
        {
            nodes.Node("Machines/Machine1/Start")
                .OnCall(StartMachineAsync);

            nodes.Variable<double>("Machines/Machine1/Temperature")
                .OnRead(ReadTemperature);
        });

Standard Method argument children are bound to their typed NodeState properties during import. A NodeSet2 Method's InputArguments and OutputArguments Variables populate MethodState.InputArguments and MethodState.OutputArguments, so normal Call argument validation uses the declarations from the document. Binding uses the authored HasProperty relationship, declared either on the Method or as an inverse reference on the argument Property; ParentNodeId is optional. Local namespace-URI reference targets are resolved against the import context's namespace table. The Property must use the namespace-zero standard BrowseName, PropertyType, the Argument DataType, and a one-dimensional value rank. Ambiguous or conflicting declarations and custom or malformed properties do not bind the Method's typed signature; their authored nodes and references are retained. Other authored reference types are preserved.

Group of dependent NodeSets

Register multiple NodeSet2 sources that depend on each other. The factory resolves the import order automatically from the RequiredModel declarations in each document.

services.AddOpcUa()
    .AddServer(o => { /* … */ })
    .AddRuntimeNodeSet(options =>
    {
        options.Sources =
        [
            RuntimeNodeSetSource.FromFile("Models/Opc.Ua.Di.NodeSet2.xml"),
            RuntimeNodeSetSource.FromFile("Models/MyMachine.NodeSet2.xml")
        ];
        options.DefaultNamespaceUri = "urn:example:MyMachine";
        options.Configure = nodes =>
        {
            nodes.Node("Machines/Machine1/Start").OnCall(StartMachineAsync);
        };
    });

Custom stream source

Use RuntimeNodeSetSource.FromStream when you want to open the NodeSet2 document lazily — for example from a database, a blob store, or an assembly resource. The delegate is called for each startup load or live generation and must return a fresh, readable Stream each time.

services.AddOpcUa()
    .AddServer(o => { /* … */ })
    .AddRuntimeNodeSet(options =>
    {
        options.Sources =
        [
            RuntimeNodeSetSource.FromStream(
                name: "MyMachine",
                openStream: ct => OpenNodeSetStreamAsync(ct),
                modelNamespaceUris: ["urn:example:MyMachine"])
        ];
    });

Direct factory registration

If you prefer to create the factory manually — for example to inject it into an existing StandardServer subclass — construct a RuntimeNodeSetNodeManagerFactory directly:

var factory = new RuntimeNodeSetNodeManagerFactory(new RuntimeNodeSetOptions
{
    Sources = [RuntimeNodeSetSource.FromFile("Models/MyMachine.NodeSet2.xml")]
});

// In a StandardServer subclass constructor:
AddNodeManager(factory);

Stream ownership contract

When FromStream is used, the runtime loader calls the openStream delegate while each NodeManager generation is created and closes the returned stream after deserialization. You must ensure that:

1. Each call to openStream returns a new stream positioned at the beginning.
2. The stream is readable and contains a valid NodeSet2 XML document.
3. You do not close the stream yourself; the factory disposes it after UANodeSet.Read.

If the delegate returns null or the stream does not contain valid NodeSet2 XML, server startup fails with a clear InvalidOperationException that names the source.

Default namespace for unqualified browse paths

When the Configure callback uses browse paths without an explicit ns=N; prefix (for example "Machines/Machine1/Start"), the runtime loader must know which namespace index to apply for the first path segment. The resolution is:

1. If RuntimeNodeSetOptions.DefaultNamespaceUri is set, that URI is used.
2. Otherwise the factory infers the unique leaf model — the one model in the loaded group that is not required by any other included source.
3. If inference is ambiguous (multiple leaf models and a Configure callback is present), startup fails with an error message that lists the candidates. In this case, set DefaultNamespaceUri explicitly.

When no Configure callback is registered, DefaultNamespaceUri has no effect and may be omitted.

Dependency sorting

The factory reads the Models/Model/RequiredModel entries from each parsed NodeSet document and performs a topological sort (Kahn's algorithm) before importing. Import order guarantees that a required model's nodes are in the address space before any document that depends on them imports its nodes.

All documents of one manager are parsed into a single batch whose parent-child relationships are linked exactly once, after the last document has been parsed. A node may therefore declare a ParentNodeId that lives in another document of the group regardless of the order the two were parsed in; a duplicate NodeId across documents is rejected while parsing. A fluent Configure callback can add further documents to the manager with builder.Import — see Importing a NodeSet2 overlay at runtime.

Dependencies on models not included in the group — for example the OPC UA base namespace or a third-party model hosted by a generated NodeManager — are silently allowed and treated as external. The server resolves cross-manager references through the normal AddReverseReferencesAsync mechanism.

Referencing a Node another NodeManager owns

A NodeSet may declare a Reference whose other endpoint belongs to a different NodeManager — an inverse Organizes placing an Object under a folder some other model defines, for instance. OPC 10000-3 requires such a Reference to be visible from both ends, so the forward edge has to appear on a Node this NodeManager does not own.

That works in both registration orders. At startup the master collects every NodeManager's external references first and applies them afterwards, so creation order does not matter. A NodeManager added after startup has no such second phase, so the master retains the startup references and each dynamic NodeManager's references, and replays them to any NodeManager registered later. Without that replay a Reference into a NodeManager that did not exist yet would simply be dropped — a reference to an absent Node is discarded rather than queued — leaving the two ends permanently disagreeing: the target browses to the source, the source does not list the target.

Both orders are pinned by RuntimeNodeSetCrossSourceReferenceTests.

Cycles among the included sources cause InvalidOperationException at startup with an error message that lists the participating sources.

Complex types

Runtime complex type loading (structures, enumerations, union types) is on by default and requires no extra configuration. After all NodeManagers have built their address spaces, StandardServer.OnNodeManagerStartedAsync scans every DataType node whose DataTypeDefinition attribute is populated and registers a NativeAOT-safe stand-in encodeable in the server's factory. The same stand-ins are reused for client decode/encode via the OPC UA Part 6 binary protocol.

You can tune this behaviour through the existing ServerComplexTypeOptions:

services.AddOpcUa()
    .AddServer(o => { /* … */ })
    .AddRuntimeNodeSet("Models/MyMachine.NodeSet2.xml")
    .AddComplexTypeSystem(o => o.Enabled = false); // disable if not needed

Setting StandardServer.LoadComplexTypes = false or disabling the complex type system entirely suppresses the stand-in loading without producing a warning. No second complex-type loading path is introduced by the runtime NodeSet feature.

For a complete description of the server-side complex type system, see ComplexTypes.md.

Comparison with source-generated NodeManagers

Aspect	Runtime NodeSet (AddRuntimeNodeSet)	Source-generated ([NodeManager])
Node access in callbacks	Generic NodeState / BaseVariableState via untyped browse paths	Strongly typed, compiler-checked fluent accessors per node
Compilation required on model change	No — reload through INodeManagerLifecycle	Yes — regenerate and rebuild
AOT / trimming compatibility	Full (uses the existing UANodeSet.Read XmlSerializer path)	Full (generated code is static)
Named NodeId constants	Not generated	Generated (Variables.*, Objects.*, etc.)
Multiple namespaces in one manager	Yes — group multiple sources	One namespace per generator run
DI registration	AddRuntimeNodeSet(...)	AddNodeManager<TFactory>()
Stream / file input	Files and custom stream factories	MSBuild AdditionalFiles only

Source-generated managers are the recommended path for production code where type safety and compile-time validation matter. Runtime NodeSets are the recommended path for rapid prototyping, model-file delivery scenarios, and cases where the XML content changes independently of the server binary.

Related documentation

• Source-Generated NodeManagers — strongly typed alternative.
• Dependency Injection — IOpcUaServerBuilder and service registration.
• ComplexTypes.md — server-side complex type loading and client-side decoding.