---
id: DATA-6
family: RT-DATA
level: core
profiles: [runtime]
posture: normative-target
added: "1.0"
changed: "1.0"
source: https://flowdrop.io/spec/rules/rt-data/data-6
specification: FlowDrop Workflow Specification 1.0-draft
licence: CC BY 4.0
---

# DATA-6 — Initial data fills a node's ports only where no edge did

*RT-DATA (Part II) · level: core · profiles: runtime · added in 1.0*

## The rule

> **Normative.** This is the rule.
>
> 1. Initial data supplied with a run, keyed by node identifier, fills that node's input ports underneath anything an edge delivered: an edge-delivered value wins, including an edge-delivered `null`.
>
> 2. An entry keyed for another node, or one that is not a map of port names to values, is ignored.


## What it means

Initial data is a fallback, not a second source competing with an edge: it
only ever fills the ports an edge left untouched. An edge-delivered `null`
still counts as delivered, so it still wins over a seeded value at the same
port — the merge is keyed on presence, not on usefulness. An entry keyed for
a node other than the one running is ignored outright, and an entry that is
not itself a map of port names to values is dropped rather than merged in
some other shape.

## Example

A node's `message` port is fed by an edge; its `seed` port is not. Initial
data carries a value for both ports, keyed to this node.

```json title="What the run's initial data offers this node" verdict="offered"
{"message": "from_initial_data", "seed": "only_in_initial_data"}
```

```json title="What the node actually receives" verdict="merged"
{"message": "from_edge", "seed": "only_in_initial_data"}
```

The wired port keeps the edge's value; the unwired one takes the seed. Where
the edge instead delivers an explicit `null` on `message`, the node still
receives `{"message": null}` — the seed does not get a second chance because
the delivered value happens to be empty.

## Related rules

- Names: DATA-1
- Referenced by: DATA-1

---

Rule identifiers are permanent and are never renumbered. This specification carries
no implementation status: each implementation publishes its own standing against
these rules. Licensed CC BY 4.0.