---
id: EXPO-2
family: GR-EXPO
level: core
profiles: [storage-api]
posture: normative-target
added: "1.0"
changed: "1.0"
source: https://flowdrop.io/spec/rules/gr-expo/expo-2
specification: FlowDrop Workflow Specification 1.0-draft
licence: CC BY 4.0
---

# EXPO-2 — An instance override decides exposure; otherwise the default does

*GR-EXPO (Part I) · level: core · profiles: storage-api · added in 1.0*

## The rule

> **Normative.** This is the rule.
>
> 1. A port is exposed on a node instance when the instance's direction-scoped overrides in `data.config.ports` contain an entry for that port carrying an `exposed` key: that key's value is the answer.
>
> 2. Where there is no such entry, or the entry carries no `exposed` key, the port's default exposure decides (`exposedByDefault`, CFG-2).


## What it means

Being named in the direction-scoped overrides is not, by itself, an override.
An entry for a port can exist there for reasons that have nothing to do with
exposure, so the only thing that flips a port away from its default is that
entry carrying an `exposed` key. A port named but silent on `exposed` reads
exactly as a port not named at all.

## Example

The port `value` defaults exposed; `error` defaults hidden (EXPO-4). Three
override shapes for `value` land on two different answers.

```json title="An override entry with an explicit exposed: false" verdict="hidden"
{ "id": "value", "exposed": false }
```

```json title="An override entry with an explicit exposed: true, on a port that defaults hidden" verdict="exposed"
{ "id": "error", "exposed": true }
```

```json title="An entry naming value, but with no exposed key at all" verdict="exposed"
{ "id": "value" }
```

The third entry names the same port as the first, and still resolves to the
default: naming a port is not deciding about it.

## Related rules

- Names: CFG-2, EXPO-1, EXPO-3, EXPO-4
- Referenced by: EXPO-1, EXPO-3, EXPO-4, EXPO-13, EXPO-15

---

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.