shopdb-flask/docs/adr/ADR-001-asset-as-platform-contract.md

ADR-001: Asset model is the platform contract

• Status: ACCEPTED
• Date: 2026-05-08
• Deciders: cproudlock
• Supersedes: none

Context

shopdb-flask is being shaped as a framework that sister GE Aerospace facilities can adopt. The framework defines a stable core; sites install plugins for the asset classes they care about (equipment, computers, printers, measuring tools, network gear, etc.).

The codebase ran two parallel object models:

1. Legacy Machine model in shopdb/core/models/machine.py. Original schema inherited from the classic-ASP shopdb. Tables: machines, pctypes, machinetypes. Plugins like printers stored extension data via PrinterData keyed by machineid.
2. New Asset model in shopdb/core/models/asset.py. Generic asset abstraction with AssetType, AssetStatus, AssetRelationship. Plugins also exposed asset-based tables keyed by assetid.

For the framework to be adoptable, the platform contract has to be one model, documented, versioned, and stable.

Decision

Asset is the platform contract. Plugin authors target the asset-based API. The Machine model and its dependents (PCType, MachineType, PrinterData keyed by machineid) are legacy and will be retired through a tracked migration.

Platform contract surface

The following are the public, versioned surface. Plugin authors may depend on them. Breaking changes require a major version bump per ADR-002.

Models

• Asset (core entity)
• AssetType (asset classification, registered by plugins)
• AssetStatus (active / inactive / decommissioned / retired)
• AssetRelationship + RelationshipType (cross-plugin links)
• Vendor, Location, LocationType, BusinessUnit, Model, OperatingSystem (shared reference data)

Helpers

• AuditLog API: audit_log(action, entitytype, entityid, ...) for plugins to record audit entries with consistent schema
• Setting API: plugin.get_setting(key) and plugin.set_setting(key, value) for plugin-scoped config persisted via the core Setting model
• resolve_asset_position(asset) for the documented position-resolution algorithm

Import surface (shopdb.api) - expanded in contract_version 0.3.0

shopdb.api is the ONLY core module plugins may import (plus shopdb.plugins.base for the ABC). Deep imports of shopdb.core.*, shopdb.extensions, or shopdb.utils.* are contract violations enforced by the test_plugins_only_import_contract_surface test. The surface re-exports:

• Infrastructure: db, cache
• Model bases: BaseModel, AuditMixin
• Core models: Asset, AssetType, AssetStatus, Vendor, Model, Communication, CommunicationType, Location, Setting, AuditLog, Application, AppVersion, OperatingSystem
• Responses: success_response, error_response, paginated_response, ErrorCodes
• Pagination: get_pagination_params, paginate_query
• Helpers: audit_log, resolve_asset_position; legacy employee_connection

Adding a name here is a minor (additive) contract change; removing one is major.

Plugin contract

• BasePlugin ABC and its hooks (search, navigation, dashboard, relationships, collector schema + apply_collector_payload)

Excluded from the contract for v1

• Event bus (get_event_handlers removed from BasePlugin). Add later if a real use case appears.

Relationship types (seeded core values)

RelationshipType is seeded with three rows. Plugin authors do not add new types in v1.

Type	Meaning	Boundary rule
partof	Composition, siblings, sub-assemblies	Parent dies without it
controls	One asset has operational authority over another	PC commands a machine, measuring tool, etc.
connectedto	Network or data link without operational authority	Cable, switch port, NAS mount

AssetRelationship columns

AssetRelationship
- relationshipid          PK
- sourceassetid           FK to assets
- targetassetid           FK to assets
- relationshiptypeid      FK to relationshiptypes (one of partof, controls, connectedto)
- label                   text, free description (e.g., "ethernet PoE", "DNC feed")
- inheritsposition        bool, true means resolved-position walk follows this edge
- propagatesthroughid     FK to relationshiptypes, nullable, see propagation below
- notes                   text
- isactive                bool
- createddate, modifieddate

Free-text label carries the domain nuance (controls with label "DNC feed" vs controls with label "operator workstation"). Avoids inflating the type list.

Sibling propagation

When a relationship is created or deleted, the framework checks RelationshipType.propagatesthroughid. If set, it finds all assets related to the source via the propagation type and applies the same change.

Default seeding:

RelationshipType	propagatesthroughid
partof	null (the propagation rail itself)
controls	partof (controls relationships propagate across siblings)
connectedto	null (network paths don't propagate)

Cycle protection: max walk depth 3, visited-set during traversal.

Position resolution

Resolved map position for any asset follows this priority chain:

1. Asset-specific override (assets.mapx, assets.mapy if non-null)
2. Walk relationships where inheritsposition=true, ordered by relationship type priority (partof first, then controls), recursively resolve the related asset's position with cycle detection
3. Fall back to the asset's location coords (locations.mapx, locations.mapy via assets.locationid)
4. If none of the above, asset is "unplaced" and rendered in a tray, not on the map

API exposes resolved position with a source indicator: {"mapx": 234, "mapy": 567, "positionsource": "self|related|location|none"}.

Hierarchical locations

locations is extended with parentlocationid (self-FK, nullable). Sites define their own location tree (cells, sub-cells, network closets, meeting rooms, labs).

locationtypes lookup is added with seeded values: section, cell, subcell, meetingroom, lab, office, storage, hallway, networkcloset, building. Sites can extend.

Asset-to-location is the existing assets.locationid FK only (single primary location for v1). Multi-location and transient placement are deferred.

Migration scope (narrowed)

Only one class of legacy data migrates: physical manufacturing equipment with a machinenumber (5-axis mills, lathes, broachers, heat treatment, CMMs, etc.).

Migration filter:

SELECT * FROM legacy.machines
WHERE category = 'Equipment'
  AND machinenumber IS NOT NULL

Rows without machinenumber: skipped. Add manually post-migration if any matter.

Migrated rows become assets with assettype='Equipment' plus a row in the equipment plugin's equipment table. Legacy machinetypeid is preserved on the equipment row to enable later reclassification (some "Equipment" rows are actually measuring tools, see ADR-005).

Skipped from migration:

• PCs (rebuilt via PXE collector pipeline, see ADR-006)
• Printers, USB devices, network gear, notifications, KB articles (operational or re-collectable, decision per class deferred until needed)

Consequences

Positive

• Plugin authors at sister sites have a single, documented contract to target
• Cross-plugin features (relationships, search, map) work uniformly
• Three relationship types are easy to learn; free-text label captures nuance
• Sibling propagation handles dual-path machines without code changes per use case
• Position resolution gives users one map without per-plugin map code

Negative

• Migration of equipment data must run cleanly; migrating-asset-schema skill owns the procedure
• Frontend views/machines/ will be repointed or replaced; effort tracked in Phase 5
• Legacy core/api/machines.py (641 LOC) becomes deprecated; deletion or shim deferred until equipment is migrated

Neutral

• Machine, PCType, MachineType, PrinterData remain in the schema until the migration completes, behind a deprecation notice. New code does not touch them.

Alternatives considered

1. Keep both models indefinitely. Doubles test surface, confuses contract docs, breaks cross-plugin features. Rejected.
2. Make Machine the contract; retire Asset. Machine has shop-floor-specific assumptions that don't generalize. Rejected.
3. Define a higher abstraction above both. Yet another layer. Asset is already the abstraction. Rejected.
4. More relationship types (controls, operates, monitors, dncfeeds, mountedon, connectedvia, inspects, siblingbay). Eight types proved unwieldy. Collapsed to three with free-text labels and per-row inheritance/propagation flags.

Open questions deferred

• Lifecycle relationship type (replaces, replacedby). Add when first needed.
• Multi-location asset placement, transient placement (calibration trip, off-site repair). Add when first needed.
• Map editing UI (drag locations onto floor plan). Phase 6 polish.
• Plugin-extensible relationship types beyond the three seeded. Add when a real cross-plugin case can't be expressed via labels.

References

• shopdb/core/models/asset.py
• shopdb/core/models/machine.py (legacy, deprecated)
• shopdb/plugins/base.py
• ADR-002 (versioning of the surface)
• ADR-003 (plugin distribution)
• ADR-004 (deployment topology)
• ADR-005 (equipment vs measuring tools split)
• ADR-006 (collector contract pattern)