2.3 DAG Execution Model

Node Output Schema

Every DAG node produces output in this schema:

{
  "text": "primary textual output (max 16 KB)",
  "artifacts": {
    "code": "optional code string (max 64 KB)",
    "metadata": {}
  }
}

DataRef Syntax

Nodes reference earlier outputs using DataRef patterns:

"${<step_id>.output.<field_path>}"

Examples:

• "${step_1.output.text}" — text output from step_1
• "${step_2.output.artifacts.code}" — code artifact from step_2

Execution Contract

The validator executor follows these 5 steps:

1. Topological sort — derive execution plan from edges. Nodes with no shared dependency run concurrently in the same execution tier.
2. Store outputs — after each node completes, store result in context[node_id].
3. Resolve DataRefs — before executing node K, resolve ${...} patterns referencing completed upstream nodes.
4. Budget ceiling check — before dispatching each node:

   budget_ceiling = min(constraints["max_budget_tao"],
                        1.5 * workflow_plan["total_estimated_cost"])
   if cumulative_tao >= budget_ceiling:
       for node in remaining_nodes:
           context[node.id] = {"status": "budget_abort", "output": None}
       break

5. Failure propagation — if a referenced field doesn't exist or the upstream node failed, current step is marked a hard failure.

Parallel DAG Rules

Metric	Sequential DAG	Parallel DAG
completion_ratio	steps_completed / total_nodes	steps_completed / total_nodes (same)
S_latency	wall-clock end-to-end	wall-clock end-to-end (parallel compresses it)
S_cost	sum of all step costs	sum of all step costs (both charged)
DataRef failure propagation	upstream fail → downstream fails	only if specific referenced node failed

Example: A→C and B→C (A and B independent). A completes, B fails. C only needs ${A.output.text}. C proceeds; B's failure reduces completion_ratio by 1/3 but does not block C.

Miners must not implement their own DataRef resolvers. All resolution is performed by the validator executor.

---

Navigation

← Previous	2.2 WorkflowSynapse Protocol
→ Next	3.1 Emission Structure
Index	Documentation Index