UA-.NETStandard/Docs/CoreNodeManagerVsCustomNodeManager2.md

CoreNodeManager vs CustomNodeManager2

This document outlines the key differences in behavior and implementation between CoreNodeManager and CustomNodeManager2 within the OPC UA .NET Standard Stack.

CoreNodeManager is typically used for managing the internal nodes of the Server (Namespace 0) or simple static node sets. CustomNodeManager2 is designed as a base class for developers implementing custom node managers with specific business logic, dynamic behavior, or backing stores.

1. Storage & Data Structures

Feature	CoreNodeManager	CustomNodeManager2
Node Storage	Uses a NodeTable (m_nodes) internally.	Uses a NodeIdDictionary<NodeState> (PredefinedNodes).
Node Type	Manages ILocalNode interface objects.	Manages NodeState objects (and subclasses).
Handle Type	GetManagerHandle returns the ILocalNode instance directly.	GetManagerHandle returns a NodeHandle wrapper containing the NodeState and validation status.
Locking	Uses DataLock (object).	Uses Lock (object).
Namespace	Typically manages dynamic nodes in specific indexes or internal server nodes.	Designed to manage specific namespaces passed in the constructor. Uses IsNodeIdInNamespace checks.

2. Extensibility

Feature	CoreNodeManager	CustomNodeManager2
Design Intent	Sealed-like behavior. Not primarily designed for inheritance or overriding behavior.	Highly extensible. Most methods (Read, Write, Browse, Call) are virtual to allow custom overrides.
Node Factory	Does not implement INodeIdFactory.	Implements INodeIdFactory to generate new NodeIds for the system context.
Address Space	CreateAddressSpace is often empty (ImportNodes is used instead).	CreateAddressSpace invokes LoadPredefinedNodes to load nodes from resources/assemblies.

3. Operational Behavior

Reading & Writing

• CoreNodeManager:
  • Read: Directly invokes ILocalNode.Read.
  • Write: Performs basic type checking (expected data type/value rank) and invokes ILocalNode.Write.
• CustomNodeManager2:
  • Read: Validates the node handle, supports operation caching, and invokes NodeState.ReadAttribute. Handles timestamp synchronization (e.g., matching ServerTimestamp to SourceTimestamp for Value attributes).
  • Write:
    • Performs Range Checks for AnalogItemState (InstrumentRange).
    • Generates Audit Events (Server.ReportAuditWriteUpdateEvent).
    • Detects Semantic Changes (e.g., changes to EURange, EnumStrings) and updates monitored items accordingly.

Method Calls

• CoreNodeManager:
  • Browse: Iterates over references stored in ILocalNode. Basic masking and filtering.
  • Translate: Basic search through internal references.
• CustomNodeManager2:
  • Browse: Uses NodeState.CreateBrowser. Explicitly validates PermissionType.Browse. Supports Views (IsNodeInView).
  • Translate: Uses CreateBrowser to navigate path. Supports resolving targets in other node managers via unresolvedTargetIds.

4. Monitoring & Subscriptions

Feature	CoreNodeManager	CustomNodeManager2
Manager	Uses SamplingGroupManager directly.	Uses IMonitoredItemManager abstraction (defaults to SamplingGroupMonitoredItemManager or MonitoredNodeMonitoredItemManager).
Filter Validation	Validates DataChangeFilter specifically (deadband, EU Range).	Delegates validation to ValidateMonitoringFilter, supports AggregateFilter (if supported by server) and DataChangeFilter.
Events	Basic event subscription support (SubscribeToEvents checks EventNotifier bit).	Full Event Support: - Manages RootNotifiers. - Propagates events via SubscribeToAllEvents. - Implements ConditionRefresh. - Validates PermissionType.ReceiveEvents.

5. History

• CoreNodeManager:
  • HistoryRead / HistoryUpdate: Iterates nodes and returns BadNotReadable / BadNotWritable (or BadHistoryOperationUnsupported implicit). No infrastructure for history.
• CustomNodeManager2:
  • Provides scaffold methods (HistoryReadRawModified, HistoryReadProcessed, HistoryUpdateData, etc.).
  • Checks AccessLevels.HistoryRead/Write and EventNotifier.HistoryRead/Write.
  • Default implementation returns BadHistoryOperationUnsupported, but is structured for easy overriding in derived classes.

6. Security

• CoreNodeManager:
  • Checks AccessLevel, UserAccessLevel, WriteMask in Write.
  • Loads Role Permissions into metadata.
• CustomNodeManager2:
  • Explicitly calls MasterNodeManager.ValidateRolePermissions during Browse, Call, and Event processing.
  • Reads and caches validation attributes (AccessRestrictions, RolePermissions) for optimized access.