---
id: DATA-1
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-1
specification: FlowDrop Workflow Specification 1.0-draft
licence: CC BY 4.0
---

# DATA-1 — An edge delivers one named output port to one named input port

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

## The rule

> **Normative.** This is the rule.
>
> 1. An edge delivers a value from a named output port on its source node to a named input port on its target node.
>
> 2. Both port names are taken from the edge's endpoint handles; an endpoint that names no port delivers nothing, and neither warns nor fails the run.
>
> 3. Delivery turns on the presence of the port's key in the source node's output, not on the value being non-null: a source that emits an explicit `null` delivers `null`, and that delivered `null` outranks the target's configuration and its schema default.
>
> 4. A source that omits the key delivers nothing at all, and the target port falls through to its configuration and then to its schema default.


## What it means

What decides whether a value is delivered is whether the source's output
contains the wired key at all, not whether the value found there is useful.
Even an explicit `null` counts as delivered, and a delivered `null` still
outranks whatever the target's own configuration or schema default would
otherwise supply.

The other side of the same clause is silent absence: an edge whose handle
cannot be split into a port name — because the direction marker is missing —
names no port, and delivers nothing. Nothing is logged and the run is not
failed; the target simply falls through to its own configuration and default,
exactly as if the edge had never been drawn.

## Example

A node wires another node's `result` output to its `data` input, but the
source's actual output never carried a `result` key.

```json title="What the source node produced" verdict="produced"
{"other": "alpha"}
```

```json title="What the target's data port receives" verdict="empty"
{}
```

A handle with no `-output-`/`-input-` marker to split on behaves the same
way: the port name resolves to nothing, and nothing arrives.

## Related rules

- Names: DATA-6, DATA-7
- Referenced by: DATA-4, DATA-6, DATA-7

---

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.