UA-.NETStandard/docs/AMB.md

OPC UA Asset Management Basics (OPC 10000-110)

The Opc.Ua.AMB* packages implement OPC 10000-110, Asset Management Basics, version 1.01.1. AMB is not a model of a kind of device: it is a set of rules and building blocks that make any object of a server a manageable asset - a Device Integration device, a Machinery machine, a pump or a scale - so that an asset management system can find it, identify it, follow its health and maintenance, link it to its documentation and place it in the plant.

A server registers its assets with a sidecar node manager; a client discovers them and reads them back into records.

Contents

• Library layout
• The model
• Where an asset lives
• Quick start - server
• Quick start - client
• Server hosting
• Builder reference
• Discovery
• Health
• Maintenance
• Documentation links
• Locations, version information, classification and structure
• Conformance matrix
• Client reference
• Samples
• Testing
• Troubleshooting
• Known limitations
• Model provenance
• Generator gaps this model uncovered
• See also

Library layout

Package	Contents
Opc.Ua.AMB	The source-generated AMB model (interfaces, condition classes, the maintenance state machine, DocumentationLinksType, the reference types, RootCauseDataType, NameNodeIdDataType, AddOpcUaAMB), AmbBrowseNames, AmbConditionClass and the shared contracts MaintenanceStateKind, AssetFaultSeverity and AssetLocationKind
Opc.Ua.AMB.Server	AmbNodeManager, the asset registry IAssetManagement with its builders and handles, the configuration stores, and AddAssetManagement() / ConfigureAssetManagement()
Opc.Ua.AMB.Client	AmbClient for discovery, identification, health alarms, maintenance, documentation links, locations and structure, plus AddAssetManagementClient()

The model package depends on the base namespace only. The server and client packages use the OPC 10000-100 Device Integration building blocks AMB applies to an asset - identification, DeviceHealth, the health alarm types - so a server needs the DI namespace; registering an asset without it fails.

The model

Model URI	C# namespace	Namespaces member	Model loader
http://opcfoundation.org/UA/AMB/	Opc.Ua.AMB	AMB	AddOpcUaAMB

The NodeSet has 92 nodes. AMB defines no event types and attaches nothing to the types of other models; it defines three building blocks an application applies:

Building block	Applied to	Section
IRootCauseIndicationType with PotentialRootCauses	alarm types	9.4
IMaintenanceEventType with MaintenanceState and eight optional details	condition types	12.2
DocumentationLinksType	assets, as an AddIn (0:HasAddIn)	10.5

Its instances are the alias category Assets below 0:Aliases with AssetsByProductInstanceUri and AssetsByAssetId, and the location entry points HierarchicalLocations and OperationalLocations below 0:Locations. The fourteen condition classes (ConnectionFailureConditionClassType and so on) are listed in AmbConditionClass.

Where an asset lives

AMB concerns assets across every model of a server, while the Device Integration address space has exactly one owner (AddOpcUaDi, AddMachinery, AddPumps or AddScales). The AMB node manager is therefore a sidecar: it loads the AMB model and serves the alias categories, the location hierarchies and the server-specific types, but the assets stay in the node manager that owns them.

Everything AMB adds to an asset - DeviceHealth, alarms, maintenance conditions, the DocumentationLinks AddIn, properties - is created in that owner. The owner registers each asset with the shared IAssetManagement registry from its setup; the registry is the meeting point of the managers.

DI / Machinery / Pumps / Scales node manager       AMB node manager (sidecar)
  DeviceSet/Pump  ---- registered with ---->        Aliases/Assets/AssetsBy...
    2:DeviceHealth, 2:DeviceHealthAlarms             Locations/HierarchicalLocations
    AMB:DocumentationLinks, AssetId, ...             server-specific alarm types

Quick start - server

services.AddOpcUa()
    .AddServer(options => { /* application name, endpoints, PKI */ })
    .AddOpcUaDi()                        // or AddMachinery, AddPumps, AddScales
    .AddAssetManagement(options => options.UseFileSystemStores("amb-state"))
    .ConfigureDevicesFor<DiNodeManager>(async context =>
    {
        IDeviceBuilder<DeviceState> device = await context.CreateDeviceAsync(
            new QualifiedName("Sensor_1", context.Manager.InstanceNamespaceIndex));
        device.WithIdentification(i => i.ProductInstanceUri = "urn:acme:sensor:4711");

        await device.RegisterAsAssetAsync(
            context.GetRequiredService<IAssetManagement>(),
            asset => asset
                .WithConfigurableAssetId()
                .WithDeviceHealth(deriveFromAlarms: true)
                .WithHealthAlarm("Fieldbus", AssetHealthAlarmKind.Failure, AmbConditionClass.ConnectionFailure)
                .WithMaintenance("AnnualInspection", AmbConditionClass.Inspection,
                    details => details.PlannedDate = new DateTime(2027, 3, 1, 8, 0, 0, DateTimeKind.Utc))
                .WithDocumentationLinks(links => links
                    .Add("Manual", "https://acme.example/sensor/manual.pdf")
                    .AllowUserLinks())
                .LocatedIn(AssetLocationKind.Hierarchical, "Plant1/Hall3/Line2"),
            context.CancellationToken);
    });

Registering checks that the asset publishes a non-empty ProductInstanceUri, on the asset or in its 2:Identification group (§7). The returned IAssetHandle drives the asset at runtime:

IAssetHealthAlarm fieldbus = handle.Health!.Alarms[0];
await fieldbus.RaiseAsync(700, new LocalizedText("The fieldbus is down."),
    [AssetRootCauses.Of(cableId, new LocalizedText("Cable cut"))]);
await handle.Maintenance!.Activities[0].StartAsync();

Quick start - client

AmbClient amb = session.AssetManagement(telemetry);

foreach (NodeId asset in await amb.DiscoverAssetsAsync())
{
    AssetSnapshot snapshot = await amb.ReadAssetAsync(asset);
    Console.WriteLine($"{snapshot.Identification.ProductInstanceUri}: {snapshot.DeviceHealth}");
}

await foreach (AssetAlarmRecord alarm in amb.ObserveHealthAlarmsAsync())
{
    Console.WriteLine($"{alarm.SourceName}/{alarm.ConditionName} {alarm.Severity} {alarm.Message.Text}");
}

Server hosting

AddAssetManagement and ConfigureAssetManagement

AddAssetManagement(options => ...) registers the AMB node manager factory, the options, the shared AssetManagement registry (also as IAssetManagement) and the configuration store. It claims no DI ownership, so it is combined with the registration that does, in either order.

ConfigureAssetManagement(context => ...) runs inside the AMB node manager while it builds its address space. The context gives the manager, the registry, the fluent builder of the AMB manager and the services; use it to define location hierarchies or to register objects the AMB manager itself creates. A failing configurator aborts the start; the server reports BadInternalError and logs the cause.

Without hosting, create an AssetManagement and pass it to new AmbNodeManager(server, configuration, assetManagement).

Options

Option	Default	Meaning
InstanceNamespaceUri	urn:opcua-netstandard:amb:instances	Namespace of the alias objects and location objects
TypeNamespaceUri	urn:opcua-netstandard:amb:types	Namespace of the server-specific alarm and condition types
RequireProductInstanceUri	true	Refuse assets without ProductInstanceUri
Discovery	AssetDiscovery.All	The alias categories assets are listed in
MaxAssetIdLength	255 (at least 40)	Longest AssetId a client may write, in Unicode characters
UseServerDefinedAlarmTypes	true	Apply the AMB interfaces on server-specific types; without them the Root Causes and maintenance units are not met (see Health)
MaxDocumentationLinkLength	2048 (at least 255)	Longest link a client may write or add
MaxUserLinksPerAsset	16 (at least 2)	How many links users may add to one asset
MaxDocumentationLinkNameLength	128	Longest browse name and display name of a link a user adds
MaxDocumentationLinkDescriptionLength	1024	Longest description of a link a user adds
MaxLocationLength	1024	Longest value a client may write to a writable location Property
AuthorizeLinkEdit	authenticated users	Who may change documentation links
UseFileSystemStores(directory)	memory	Persist what clients configure below a directory

Persistence

What clients configure - the AssetId, editable and added documentation links, writable locations and the local time - is kept in an IAssetConfigurationStore under the asset's ProductInstanceUri. MemoryAssetConfigurationStore keeps it for the life of the process; FileSystemAssetConfigurationStore (UseFileSystemStores) writes one JSON file per asset and restores the values on start. A document is written to a temporary file first and then replaces the old one, so a crash leaves either the old or the complete new document. A restart has to keep the application identity, because the namespaces of persisted NodeIds are stored by URI.

When to register

Health alarms and maintenance conditions are created while the node manager that owns the asset builds its address space - from ConfigureDevicesFor, an IMachineryConfigurator, ConfigurePumps, ConfigureScales or ConfigureAssetManagement. Afterwards the fluent builder is sealed and creating them fails. Identification, discovery, links and locations work for assets registered later as well.

Builder reference

IAssetBuilder, passed to RegisterAssetAsync (and to IDeviceBuilder<T>.RegisterAsAssetAsync):

Method	Adds	Section
WithConfigurableAssetId(default)	a writable, persistent 2:AssetId	7
WithDeviceHealth(initial, deriveFromAlarms)	2:DeviceHealth, with 2:IDeviceHealthType where the type lacks it	9.2
WithHealthAlarm(name, kind, class)	an OPC 10000-100 health alarm with root causes, and 2:DeviceHealth following the alarms unless WithDeviceHealth sets it up	9.2 to 9.4
WithMaintenance(name, class, details, onStateChanged)	a maintenance condition with its state machine	12
WithDocumentationLinks(links)	the DocumentationLinks AddIn	10.5
WithVersionInformation(hardware, software, counter)	revisions and RevisionCounter	10.2
WithLocation(kind, value, writable)	HierarchicalLocation, OperationalLocation or DigitalLocation	13.3.2, 13.4.2, 13.5
WithLocalTime(offset, daylightSaving, writable)	0:LocalTime	13.2
LocatedIn(kind, "A/B/C")	membership in a location hierarchy	13.3.3, 13.4.3
ClassifiedAs(dictionaryEntry)	a 0:HasDictionaryEntry reference to a dictionary entry (DefineDictionaryEntryAsync)	11
WithRequirements(entries), WithCapabilities(entries)	the two folders	10.6, 10.7
RelatesTo(referenceType, target)	a sub-asset (hierarchical) or a relation (non-hierarchical)	14

Properties the asset publishes already are used rather than duplicated, and an existing write handler of the AssetId keeps running.

Discovery

Every registered asset with a ProductInstanceUri is listed in AssetsByProductInstanceUri, and every asset that has a 2:AssetId in AssetsByAssetId (§8.2): under its value, or as NoAssetIdAssigned while the value is empty (§8.2.3). An asset without an AssetId is not listed there. One AliasNameType object stands for each alias name and references its assets with 0:AliasFor - assets that share a name share the object (§8.1); each asset gets the inverse 0:HasAlias. FindAlias works on each of the three categories; a search on Assets covers both subcategories.

Listing, moving or withdrawing an asset changes the NodeVersion of the category and is announced with a GeneralModelChangeEvent. Writing a configurable AssetId moves the asset once the value is persisted; the writes of one asset are serialized, so the stored value, the value clients read and the alias never disagree. A ProductInstanceUri or an AssetId outside the binding that the application changes later moves the asset as well, once the change is reported through ClearChangeMasks; an asset registered without a ProductInstanceUri (RequireProductInstanceUri = false) is listed then. An AssetId that clients cannot write is logged as a warning: §7 asks for a writable one.

Health

DeviceHealth is set by the application (SetDeviceHealthAsync) or, with deriveFromAlarms: true, follows the active alarms: failure before function check before out of specification before maintenance required. An asset with health alarms always has DeviceHealth (§9.2); without WithDeviceHealth it follows the alarms. Its source timestamp changes only with the value, because it marks when the asset entered the state (§9.2).

A health alarm is an instance of an OPC 10000-100 alarm type (AssetHealthAlarmKind: Failure, CheckFunction, OffSpec, MaintenanceRequired), created on the asset so that SourceNode and SourceName identify the asset (§9.3), listed in the 2:DeviceHealthAlarms folder, and reporting an AMB condition class.

OPC 10000-110 applies IRootCauseIndicationType to alarm types. By default the manager therefore creates AssetFailureAlarmType, AssetCheckFunctionAlarmType, AssetOffSpecAlarmType and AssetMaintenanceRequiredAlarmType in its type namespace, each a subtype of the DI alarm type that implements the interface; a client filtering for the DI type still receives the alarms. UseServerDefinedAlarmTypes = false keeps the DI types and references the interface from each alarm instead; the alarm types then do not implement the interface, so the server does not claim "AMB Asset Health Status Root Causes" (§9.4.1).

RaiseAsync(severity, message, rootCauses) takes a severity of one of the active bands of OPC 10000-110 Table 15 (AssetFaultSeverities):

Severity	Category
801 to 1000	Critical fault
601 to 800	Major recoverable fault
401 to 600	Minor recoverable fault
301 to 400	Maintenance needed
201 to 300	Limited resource capacity near limit
1 to 200	Inactive

The potential root causes follow §9.4.2: no list means the cause is unknown and becomes one "unknown" entry, AssetRootCauses.Self (an empty list) means the alarm itself is the cause. ClearAsync drops the severity into the inactive band; an unacknowledged alarm stays retained until a client acknowledges it, and the acknowledgement is reported as an event.

Maintenance

A maintenance activity is a condition of the server-specific AssetMaintenanceActivityConditionType, a subtype of 2:MaintenanceRequiredAlarmType that implements IMaintenanceEventType (UseServerDefinedAlarmTypes = false: the DI type with the interface on the instance, which does not meet "AMB Current and Future Maintenance Activities", since §12.1 asks the condition type to implement it). It reports a maintenance condition class and moves through the MaintenanceEventStateMachineType:

stateDiagram-v2
    [*] --> Planned
    Planned --> Executing: StartAsync
    Executing --> Finished: FinishAsync
    Finished --> Planned: ReplanAsync

State	Condition
Planned	active, retained, severity 301
Executing	active, retained, severity 301
Finished	inactive, severity 100, retained until acknowledged

The description of MaintenanceActivityDetails is the message of the events (§12.1); a failed execution is told through the message of FinishAsync. The details (planned date, estimated downtime, supplier, qualification, replaced and serviced parts, method, configuration change) are published once they are set, and UpdateAsync changes them in any state. Every transition and update reports an event, so the event history keeps planned and actual values apart. A transition the state machine does not allow - starting a finished activity, for example - fails with BadInvalidState, and so does one a handler on OnBeforeTransition of the MaintenanceState refuses. Those handlers, the one on OnAfterTransition and the delegate of UpdateAsync run outside the lock of the activity, so they may read it; a transition whose activity moved while its guard ran is refused. An onStateChangedAsync callback ties the activity to the application, for example to switch a machine into its Maintenance operation mode, as the sample does.

Documentation links

WithDocumentationLinks adds the AddIn AMB:DocumentationLinks:

• Add(name, uri) - a link of the manufacturer; read only.
• AddEditable(name, default) - a link users change to one of their own ("AMB DocumentationLinks Edit Base").
• AllowUserLinks() - the AddLink and RemoveLink methods ("AMB DocumentationLinks Edit Advanced").

AddLink persists the link before it creates the variable, and the variable keeps its NodeId across restarts; since §10.5.3 asks for that, AllowUserLinks() needs a persistent store - with the memory store, registering the asset fails with BadConfigurationError. RemoveLink removes only links AddLink created. An editable link nobody has set is published as null and, like a cleared one, does not count for "AMB DocumentationLinks Base". Both answer with BadUserAccessDenied and BadInvalidArgument as §10.5 defines; AddLink refuses names, display names and descriptions longer than the options allow. Links restored after a restart are cut to the limits then in force, with a warning in the log, and the stores refuse any value longer than AssetConfigurationNames.MaxValueLength. AuthorizeLinkEdit decides who may write, add and remove links; by default every authenticated user may and an anonymous one may not. The UserAccessLevel of an editable link and the UserExecutable of AddLink and RemoveLink show a user who may not change links that he cannot.

OPC 10000-110 gives a client no way to tell the links of the manufacturer from the ones users added, although RemoveLink accepts only the latter. §10.5.1 lets vendors add Properties with metadata to the links, so every link AddLink created - and only such a link - carries the Boolean Property UserLink (DocumentationLinkProperties.UserLink) with the value true. Its browse name is qualified with the namespace of the server-specific types (AmbServerOptions.TypeNamespaceUri), not with the AMB namespace, and its NodeId follows from the link's, so it is the same after a restart. DocumentationLinkRecord.IsUserLink reports it on the client, which compares the name only, as the namespace is configurable.

Locations, version information, classification and structure

LocatedIn(kind, "Plant1/Hall3/Line2") creates the levels below HierarchicalLocations or OperationalLocations in the AMB manager - the first organized by the entry point, deeper ones as components, as §13.3.3 recommends - and connects the deepest level and the asset with HierarchicalContains or OperationalContains in both directions (§13.1). IAssetManagement.DefineLocationAsync creates a location without an asset. Unregistering an asset removes the *Contains references; the locations stay.

The version information writes the hardware and software revisions and the RevisionCounter onto the properties the asset has and creates the missing ones; IAssetHandle.IncrementRevisionCounterAsync counts configuration changes. A Device Integration device has all three properties, but their OPC 10000-100 defaults - empty revisions and a RevisionCounter of -1 - say that the device does not provide them and do not count as version information. Asking for version information starts a counter of -1 at 0.

Requirements and capabilities are folders in the AMB namespace whose entries may reference entries of external dictionaries such as IEC CDD or ECLASS; ClassifiedAs classifies the asset itself. OPC 10000-19 asks the target of HasDictionaryEntry to be a DictionaryEntryType object: IAssetManagement.DefineDictionaryEntryAsync(irdi) creates an IrdiDictionaryEntryType object below Server/Dictionaries whose NodeId is the IRDI in the namespace http://opcfoundation.org/UA/Dictionary/IRDI (AmbServerOptions.IrdiNamespaceUri), so an asset is classified with new ExpandedNodeId(irdi, AmbServerOptions.IrdiNamespaceUri), before or after the entry is defined. "AMB Classification" counts only such references. RelatesTo with a hierarchical reference makes a sub-asset, with a non-hierarchical one - 0:Utilizes, 0:IsPhysicallyConnectedTo and the other OPC 10000-23 references - a relation; the target gets the inverse reference.

Conformance matrix

Server

The manager advertises the conformance units the registered assets meet, and the AMB Base Asset Management Server Facet (http://opcfoundation.org/UA-Profile/AMB/Server/BaseServer) exactly when its only mandatory unit, AMB Asset Identification, is met; the other 27 units are optional (§15.2). A unit whose rule reads "every asset" is met only with at least one asset registered. The units are qualified names in namespace 0, as Device Integration and Machinery publish theirs. The capabilities describe the current configuration (OPC 10000-5 §6.3.2): registering or unregistering an asset publishes the list again, with the units and the facet the assets meet now, so a unit they no longer meet is withdrawn.

In the Tests column, "session" means a test checks the unit through a real client session, "in-process" that a test checks it inside the server only.

Conformance unit (Table 54)	Status	Rule the server applies	Tests
AMB Asset Identification (mandatory)	Implemented	every asset has a ProductInstanceUri, on the asset or in 2:Identification	session
AMB Configurable Asset Identification	Implemented	every asset has a writable AssetId of at least 40 characters, and the store is persistent	session
AMB Asset Discovery by ProductInstanceUri	Implemented	every asset is listed in the category	session
AMB Asset Discovery by AssetId	Implemented	every asset with an AssetId is listed in the category, and at least one has one	session
AMB Asset Health Status Base	Implemented	every asset has 2:DeviceHealth	session
AMB Asset Health Status Alarms	Implemented	every asset has a health alarm	session
AMB Asset Health Status Root Causes	Implemented	as Alarms; the alarm types implement IRootCauseIndicationType (UseServerDefinedAlarmTypes)	session
AMB Asset Health Status Alarm Categories	Implemented	as Alarms; every alarm reports a condition class	session
AMB Asset Health Tracking Overall Asset Status	Not implemented yet (history)	-	-
AMB Asset Health Tracking Events	Not implemented yet (history)	-	-
AMB Version Information	Implemented	every asset has a non-empty hardware or software revision and a RevisionCounter of at least 0	session
AMB Operation Counters	Inspected only; AMB defines no counters (§10.3)	an asset has 2:OperationCounters with a counter	in-process
AMB DocumentationLinks Base	Implemented	an asset has a link with a value	session
AMB DocumentationLinks Edit Base	Implemented	every asset has an editable link of at least 255 characters, and the store is persistent	session
AMB DocumentationLinks Edit Advanced	Implemented	every asset has AddLink and RemoveLink and room for two links of at least 255 characters, and the store is persistent	session
AMB Requirements	Implemented	an asset has a Requirements folder with an entry	session
AMB Capabilities	Implemented	an asset has a Capabilities folder with an entry	in-process
AMB Classification	Implemented	an asset has a HasDictionaryEntry reference to a dictionary entry object (OPC 10000-19)	session
AMB Current and Future Maintenance Activities	Implemented	every asset has a maintenance activity, and the condition type implements IMaintenanceEventType (UseServerDefinedAlarmTypes)	session
AMB Past Maintenance Activities	Not implemented yet (history)	-	-
AMB Local Time	Implemented	an asset has 0:LocalTime	session
AMB Hierarchical Location Property	Implemented	an asset has the property	session
AMB Hierarchical Location Objects	Implemented	an asset is contained in a hierarchical location	session
AMB Operational Location Property	Implemented	an asset has the property	in-process
AMB Operational Location Objects	Implemented	an asset is contained in an operational location	in-process
AMB Digital Location	Implemented	an asset has the property	in-process
AMB Sub-assets	Implemented	an asset has another asset below it	session
AMB Asset relations	Implemented	an asset has a non-hierarchical reference to another asset	session

The unit and facet names follow Tables 54 to 56 of the specification. The profile database has no AMB entries yet (checked on 2026-10-01).

Client

A client does not advertise conformance units; the table says which calls of AmbClient serve the client units of OPC 10000-110 and the AMB Base Asset Management Client Facet (http://opcfoundation.org/UA-Profile/AMB/Client/BaseClient), whose only mandatory unit is AMB Client Asset Identification.

Client conformance unit	Status	Calls
AMB Client Asset Identification (mandatory)	Implemented	ReadIdentificationAsync
AMB Client Asset Discovery by ProductInstanceUri	Implemented	FindAssetsAsync, EnumerateAssetsAsync
AMB Client Asset Discovery by AssetId	Implemented	FindAssetsAsync, EnumerateAssetsAsync
AMB Client Asset Health Status	Implemented	ReadDeviceHealthAsync, ReadHealthAlarmsAsync, ObserveHealthAlarmsAsync
AMB Client Asset Health Tracking Status	Not implemented yet (history)	-
AMB Client Current and Future Maintenance Activities	Implemented	ReadMaintenanceActivitiesAsync, ObserveMaintenanceAsync
AMB Client Past Maintenance Activities	Not implemented yet (history)	-
AMB Client sub-assets	Implemented	EnumerateSubAssetsAsync
AMB Client sub-assets remote	Partly: an asset of another server is reported, not followed	EnumerateSubAssetsAsync

Client reference

AmbClient is created with session.AssetManagement(telemetry) or through AddAssetManagementClient() (an AmbClientFactory and a Func<CancellationToken, Task<AmbClient>>). It registers the AMB data types with the session.

For bounded interactive reads, opt into the strict constructor:

var assets = new AmbClient(session, telemetry, new AmbClientOptions
{
    MaximumBrowseReferences = 1024,
    MaximumBrowsePages = 128
});
AssetIdentificationRecord identity = await assets.ReadIdentificationAsync(assetId, cancellationToken);
foreach (AssetReadValue field in identity.Values)
{
    // IsAbsent identifies a missing optional browse path, not a failed value read.
    Console.WriteLine($"{field.SourceNodeId}: {field.Value.StatusCode}");
}

Hosted clients can use the same immutable options:

services.AddOpcUa()
    .AddClient(options =>
    {
        options.ApplicationName = "AssetClient";
        options.ApplicationUri = "urn:localhost:AssetClient";
    })
    .AddAssetManagementClient(new AmbClientOptions
    {
        MaximumBrowseReferences = 1024,
        MaximumBrowsePages = 128
    });

Both AmbClientFactory.CreateAsync and the registered Func<CancellationToken, Task<AmbClient>> apply these limits. Alternatively, register an AmbClientOptions singleton before resolving the factory, or pass options directly to the three-argument AmbClientFactory constructor. Without options, the existing factory and builder APIs retain tolerant behavior. Invalid limits are rejected before the factory opens a session.

Strict traversal limits apply while collecting pages and walking the asset graph. Reads are batched, and returned records expose source identity, browse path and the original DataValue in Values. Non-Good and wrongly typed reads throw AmbValueReadException, whose ReadValue retains the original evidence. A missing optional path has IsAbsent == true; a present Good-null value does not, including a typed null ExtensionObject in a structure field such as LocalTime or MaintenanceSupplier. Scalar fields still require their expected value type. The existing constructor retains its tolerant behavior.

Strict condition inspection requires DeviceHealthAlarms and does not start an implicit condition-refresh subscription. The existing event-observation methods retain their documented stream semantics and do not populate the read-specific Values evidence. Transport quotas still bound incoming message/value sizes; the traversal options are not additional byte quotas.

Event observation falls back to known maintenance classes when subtype browsing is denied or reaches a traversal limit. An incomplete class set is not cached, so a later strict address-space read retries discovery and reports its failure.

Category NodeVersion describes alias-set changes, not an asset-wide metadata ETag. A caller preparing an edit must also revalidate current alias membership, the exact edit target, permissions and relevant old value. The client does not provide atomic compare-and-swap.

Area	Calls
Discovery	FindAssetsAsync(pattern, category), EnumerateAssetsAsync(category), DiscoverAssetsAsync, ReadNodeVersionAsync, ObserveAssetSetChangesAsync
Identification	ReadIdentificationAsync (on the asset, then in 2:Identification; empty values count as not set), WriteAssetIdAsync
Health	ReadDeviceHealthAsync, ReadHealthAlarmsAsync, ObserveHealthAlarmsAsync, AcknowledgeAsync
Maintenance	ReadMaintenanceActivitiesAsync, ObserveMaintenanceAsync, AcknowledgeAsync
Documentation links	ReadDocumentationLinksAsync (with IsWritable from the UserAccessLevel and IsUserLink from the UserLink Property), AddDocumentationLinkAsync, RemoveDocumentationLinkAsync, WriteDocumentationLinkAsync
Locations and structure	BrowseLocationsAsync, ReadLocationsOfAssetAsync, ReadContextAsync, ReadEntriesAsync, EnumerateSubAssetsAsync, ReadRelationsAsync
Snapshot	ReadAssetAsync

The observe calls need an IStreamingSubscription; without one they use the default streaming subscription of a ManagedSession. Both select the conditions of the notifier (ConditionType) and tell maintenance activities apart by their condition class - MaintenanceConditionClassType or a subtype, read from the server once (§12.1) - so the health and the maintenance stream each get their own events and one does not see the other's. The fields of the AMB interfaces are selected with BaseEventType, since the Device Integration types are only recommended. ReadHealthAlarmsAsync and ReadMaintenanceActivitiesAsync read the conditions an asset lists in its 2:DeviceHealthAlarms folder, and without the folder ask for a condition refresh (ManagedSession only), which reports the retained conditions of the asset. A RevisionCounter of -1, the "not supported" of OPC 10000-100, is read as not set.

Samples

Sample	Shows
AmbServer	A cooling pump and a flow sensor (DI devices) and a hydraulic press (Machinery machine) registered as assets, with every building block, file-system persistence, and a simulation of alarms and maintenance; the press switches into its Maintenance operation mode while it is serviced
AmbClient	Discovery, snapshots of every asset, the location hierarchies, AddLink and RemoveLink, writing an AssetId, and streams of health alarms and maintenance activities

See samples/AMB for how to run them.

AmbServer accepts --host, --port, an absolute --pki-root, --autoaccept true|false and an optional --run-seconds from 1 through 3600. Ordinary standalone defaults and persistent state behavior are unchanged.

Testing

dotnet test tests/Opc.Ua.AMB.Tests

Fixture	Covers
AmbModelTests, AmbContractsTests	The generated model and the contracts
AmbNodeManagerTests, AmbHostingTests, AmbCompositionTests	The manager, hosting, composition with DI and Pumps
AssetRegistrationTests, ConfigurableAssetIdTests, AssetConfigurationStoreTests	Registration, identification and the stores
AssetDiscoveryTests	The alias categories, FindAlias, NodeVersion
HealthAlarmTests, MaintenanceActivityTests, DocumentationLinksTests, AssetStructureTests	The building blocks in-process
Amb*SessionTests	Each area over a real client session
AmbClientTests	The client without a server
AmbClientServerE2eTests	AmbClient against a hosted server, a restart with persistence, and a Machinery machine as an asset

Troubleshooting

Symptom	Cause	Fix
An event field of PotentialRootCauses or MaintenanceState is always null	The select clause names the interface (IRootCauseIndicationType, IMaintenanceEventType) as its type definition; a server checks it against the type hierarchy of the event, which an interface is not part of	Select with BaseEventType as the type definition, as AmbClient does; the DI types work only for conditions that derive from them
0:Aliases/FindAlias does not find assets	The AMB categories are served through a registry of the AMB manager, not the server-wide one	Call FindAlias on Assets, AssetsByProductInstanceUri or AssetsByAssetId
BadInvalidState when registering an asset with an alarm or a maintenance activity	The owner's address space is already built and its builder sealed	Register the asset from the owner's setup (see When to register)
BadConfigurationError: the AMB node manager is not part of the server	AddAssetManagement is missing	Add it
BadConfigurationError: no Device Integration namespace	No DI owner is registered	Add AddOpcUaDi, AddMachinery, AddPumps or AddScales
BadConfigurationError: no ProductInstanceUri	The asset publishes none	Set it, or turn off RequireProductInstanceUri for an asset completed later
BadConfigurationError when registering an asset with AllowUserLinks()	The store keeps what users add in memory only (§10.5.3)	Use UseFileSystemStores or another persistent store
BadUserAccessDenied from AddLink or writing a link	Anonymous session, or AuthorizeLinkEdit refuses	Authenticate, or set AuthorizeLinkEdit
An added link or the AssetId is gone after a restart	Memory store, or a changed application identity	Use UseFileSystemStores and keep the ApplicationUri and the namespaces
"AMB Configurable Asset Identification" is not advertised	The memory store does not survive a restart	Use a persistent store
An observe call fails with BadInvalidState	No streaming subscription and no ManagedSession	Pass an IStreamingSubscription
A server shows no 0:Locations, or BrowseLocationsAsync finds nothing	0:Locations came with UA 1.05.02, and a location exists only once an asset is put into it or it is defined	AmbClient browses from HierarchicalLocations and OperationalLocations directly; on the server use LocatedIn or DefineLocationAsync

Known limitations

Topic	Behaviour	Section
Source timestamp of DeviceHealth after a restart	The timestamp marks when the asset entered its state while the server runs; after a restart it is the time of the restart, since the state is not persisted	9.2 ("should")
Optional members of a maintenance activity	Once published, a member keeps its property; UpdateAsync changes its value but does not remove it	12.2
2:PatchIdentifiers	WithVersionInformation does not create it; an asset that publishes it keeps it	10.2
Location objects	An asset is contained by the deepest level of each path it is put into, not by the levels above	13.3.3.1
Event history	"AMB Asset Health Tracking" and "AMB Past Maintenance Activities" need a historian and are left for a later change	Table 54

Model provenance

src/Opc.Ua.AMB/Model/Opc.Ua.AMB.NodeSet2.xml is the unmodified OPC Foundation publication from UA-Nodeset/latest/AMB: model version 1.01.1, published 2024-02-27, requiring UA 1.05.02. The RequiredModel version is a lower bound, not a pin.

Opc.Ua.AMB.Upstream.NodeIds.csv is the identifier table of the publication, vendored unchanged. Opc.Ua.AMB.NodeIds.csv is derived from it with tools/nodesets/derive-identifier-table.py (92 rows, 25 symbols renamed to the generator's naming, for example Aliases_Assets to Assets for the instances below namespace-0 objects) and pins the symbol-to-NodeId mapping; the generator fails the build when the two disagree.

Generator gaps this model uncovered

AMB is the first companion model that instantiates namespace-0 types at the top level (AliasNameCategoryType below 0:Aliases). That showed one new gap; two known ones apply as well:

• No identifier constants for instance children the NodeSet adds itself. The NodeVersion properties of AssetsByProductInstanceUri and AssetsByAssetId are generated correctly, but get no VariableIds constants, because the generator takes children of a top-level instance only when the type declares them as mandatory. The server finds the property through its browse name, the client through a browse path. AmbModelTests.NodeVersionHasNoIdentifierConstant records the gap and fails once the generator emits the constants. The obvious fix changes the identifiers of other generated models, among them the reference server's, and is left for a separate change.
• A child created through CreateChild is invisible to clients. As described for Pumps, the generic path creates a child without reference type, type definition and data type. When the AMB manager adds a 2:AssetId through the slot of a device type, it completes the property the way the generated helpers do.
• The generated maintenance state machine has no transition tables. Like the Machinery state machines, MaintenanceEventStateMachineState does not override StateTable, TransitionTable and TransitionMappings. The server drives it with tables built from the generated MaintenanceEventStateMachineTypeIds.

See also

• Device Integration developer guide: DiNodeManager, ConfigureDevicesFor, identification and the alarm types AMB builds on
• Alias names: the Part 17 categories AMB discovery uses
• Machinery developer guide: the machine builders; a machine becomes an asset through IMachineHandle<T>.AsNode()
• OPC 10000-110 on the OPC Foundation reference site