Spanda

Local Decision Trees

Status: Stable — tree evaluation, Ed25519 signing (spanda decision sign-tree), and cache merge.

Local decision trees encode bounded edge autonomy — conditional workflows that run on-device without central approval, within safety and trust policy limits.

Syntax

decision_tree <Name> <scope> {
    version "1.0.0";
    when <condition> {
        <actions>
        if <nested_condition> { <actions> }
        else if <nested_condition> { <actions> }
        else { <actions> }
    }
}

Scope maps to decision layer:

Scope	Layer
reflex	Layer 0 — immediate safety
local	Layer 1 — local entity
fleet, group, swarm	Layer 2 — coordination
central, cloud, control_center	Layer 3 — governance

Requirements

Decision trees must be:

• Versioned — version "1.0.0" field
• Signed — attached via policy cache signature
• Auditable — every evaluation emits a DistributedDecisionRecord
• Testable — spanda decision inspect and spanda decision simulate
• Simulatable — POST /v1/decisions/simulate
• Bounded — cannot override safety policy, kill switch, or trust blocks

Evaluation

Trees evaluate top-down: first matching when branch wins; nested if / else if / else provide sub-branching.

spanda decision inspect gps_loss.sd \
  --entity Rover001 \
  --signal "gps.status == Failed=true,visual_odometry.available=true"

Example

See examples/showcase/distributed_decisions/gps_loss_local_recovery/main.sd.

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