---
id: SCH-35
family: GR-SCHEMA
level: core
profiles: [storage-api, editor-client]
posture: normative-target
added: "1.0"
changed: "1.0"
source: https://flowdrop.io/spec/rules/gr-schema/sch-35
specification: FlowDrop Workflow Specification 1.0-draft
licence: CC BY 4.0
---

# SCH-35 — Lane derivation is total, and an undeclared port is the sink

*GR-SCHEMA (Part I) · level: core · profiles: storage-api, editor-client · added in 1.0*

"What does an undeclared port mean?" once had seven disagreeing answers. It has one: the sink.

## The rule

> **Normative.** This is the rule.
>
> 1. Every one of JSON Schema's seven type words derives a lane, and both `null` and an absent `type` resolve to the sink lane `mixed`.
>
> 2. Derivation never falls back to `string`.
>
> 3. Every reader of a port's lane gives the same answer: the derivation itself, the served default lane, the projection of a workflow's interface, and an editor's own default alike.
>
> 4. Because an undeclared port is the sink rather than a string, a caller may supply any JSON value to it, an array or null included.

## Related rules

- Names: SCH-9, SCH-10, SCH-34, SCH-40
- Referenced by: SCH-9, SCH-10, SCH-34, SCH-40

---

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.