Joseph Doherty
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2a74daf228
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ADR-002 — driver-vs-virtual dispatch: DriverNodeManager routes reads/writes/subscriptions across driver tags and virtual (scripted) tags via a single NodeManager with a NodeSource tag on NodeScopeResolver's output. Locks the architecture decision Phase 7 Stream G was going to have to make anyway — documenting it up front so the stream implementation can reference the chosen shape instead of rediscovering it. Option A (separate VirtualTagNodeManager sibling) rejected because shared Equipment folders owning both driver and virtual children would force two NodeManagers to fight for ownership on every Equipment node — the common case, not the exception — defeating the separation. Option C (virtual engine registers as a synthetic IDriver through DriverTypeRegistry) rejected because DriverInstance shape is wrong for scripting config (no DriverType, no HostAddress, no connectivity probe, no NSSM wrapper), IDriver.InitializeAsync semantics don't match script compilation, Polly resilience wrappers calibrated for network calls would either passthrough pointlessly or tune wrong, and Admin UI would need special-casing everywhere to hide fields that don't apply. Option B (single DriverNodeManager, NodeScopeResolver returns NodeSource enum alongside ScopeId, dispatch branches on source) accepted because it preserves one address-space tree with one walker, ACL binding works identically for both kinds, Phase 6.1 resilience + Phase 6.2 audit apply uniformly to the driver branch without needing Roslyn analyzer exemptions, and adding future source kinds is a single-enum-case addition. NodeScopeResolver.Resolve returns NodeScope(ScopeId, NodeSource, DriverInstanceId?, VirtualTagId?); DriverNodeManager pattern-matches on scope.Source and routes to either the driver dictionary or IVirtualTagEngine. OPC UA client writes to a virtual node return BadUserAccessDenied before the dispatch branch because Phase 7 decision #6 restricts virtual-tag writes to scripts via ctx.SetVirtualTag. Dispatch test coverage specified for Stream G.4: mixed Equipment folders browsing correctly, read routing per source kind, subscription fan-out across both kinds, the BadUserAccessDenied guard on virtual writes, and script-driven writes firing subscription notifications. ADR-001's walker gains the VirtualTag config-DB table as an additional input channel alongside Tag; NodeScopeResolver's ScopeId return stays unchanged so Phase 6.2's ACL trie needs no modification. Consequences flagged: whether IVirtualTagEngine lives in Core.Abstractions vs Phase 7's Core.VirtualTags project, and whether future server-side methods on virtual nodes would route through this dispatch, both marked out-of-scope for ADR-002.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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2026-04-20 16:08:01 -04:00 |
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