Spanda

Entity Graph

The Entity Graph is the platform-wide directed graph of all Spanda entities and their relationships. It supports traversal, dependency analysis, impact analysis, traceability, and Control Center visualization.

Structure

pub struct EntityGraph {
    pub nodes: Vec<EntityRecord>,
    pub edges: Vec<EntityRelationship>,
}

Built from EntityRegistry::graph() after build_entity_registry() projects configuration into entities.

Example hierarchy

Organization
    └── Fleet
            ├── Robot
            │     └── Compute
            │           └── Camera
            │                 └── (depends_on) Provider
            ├── Human
            │     └── (assigned_to) Wearable
            ├── Package
            └── Mission (runtime — Phase 2)

Graph operations

Operation	API / method	Use case
Full graph	GET /v1/entities/graph	Dashboard visualization
Neighborhood	Control Center entity panel	Inspect one entity and peers
Impact analysis	GET /v1/entities/{id}/relationships → impact	“What breaks if this GPS fails?”
Dependency chain	same → dependency_chain	Provider/package dependency walk
Digital thread	/v1/digital-thread/query	Program-centric trace (complementary)
Unified traceability	GET /v1/entities/traceability	Entity + program + digital-thread chain

Phase 3 (complete) aligns dependency-graph nodes with entity IDs and merges digital-thread links into the entity relationship store. Query params: entity_id, device_id, capability.

Impact analysis

EntityRegistry::impact_analysis(entity_id) traverses outgoing contains, depends_on, and consumes edges (and reverse depends_on/assigned_to) to collect affected entity IDs.

Dependency chain

EntityRegistry::dependency_chain(entity_id) walks depends_on and consumes edges from the entity outward — useful for “which provider does this device ultimately depend on?”

Relationship to other graphs

Graph	Scope	Crate
Entity graph	All configured platform objects	spanda-config
Dependency graph	Program missions, capabilities, packages	spanda-graph
Config graph	TOML layer merge order	spanda-config layer
Collaboration graph	HRI sessions	/v1/hri/collaboration

Phase 3 of the migration plan is complete: dependency nodes carry entity_id metadata and /v1/entities/traceability returns unified chains.

Visualization

Control Center: Entities tab → Graph view renders an SVG neighborhood around the selected entity.

SDK:

let graph = client.entity_graph()?;

const res = await fetch(`${base}/v1/entities/graph`);
const { graph } = await res.json();

Edge data model

Each edge:

{
  "from_id": "rover-001",
  "to_id": "gps-001",
  "kind": "contains",
  "label": "assigned"
}

See entity-relationships.md for the full relationship taxonomy.

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