---
id: CRON-1
family: RT-CRON
level: extended
profiles: [runtime]
posture: normative-target
added: "1.0"
changed: "1.0"
source: https://flowdrop.io/spec/rules/rt-cron/cron-1
specification: FlowDrop Workflow Specification 1.0-draft
licence: CC BY 4.0
---

# CRON-1 — A cleared schedule means not scheduled, and every reader says so

*RT-CRON (Part II) · level: extended · profiles: runtime · added in 1.0*

A schedule is invisible until it fires or fails to, so the component that decides a trigger is due and the one that reports when it will next run must never describe the same stored value differently. Blank-means-inactive is the reading every comparable scheduler uses.

## The rule

> **Normative.** This is the rule.
>
> 1. A trigger whose cron expression is the empty string is not scheduled: it must not fire, and a report of when it will next run must say it has none.
>
> 2. Empty means exactly empty: an expression that merely looks unfilled, such as `0`, is a malformed expression and must be reported as invalid rather than as unset, so an operator is never told to fill in a field that is already filled in.
>
> 3. Whichever component decides that a trigger is due and whichever reports its next run must reach the same conclusion about the same stored schedule.


## What it means

A cleared schedule expression is not special-cased on the way in — it is a
stored value like any other, and the component that decides a trigger is due
and the component that reports its next run must read that value the same
way. Both must treat a blank expression as "not scheduled," never as a
schedule that fires on every pass.

The clause that a careful reader misses is the second one: "blank" means
exactly blank. An expression that only looks unfilled, such as a single `0`,
is a real schedule expression the parser rejects, not an absent one.
Reporting it as absent tells whoever is debugging a dead trigger to go fill
in a field that already holds a character.

## Example

The same missing next run, reported for two different stored expressions:

```json title="The reported code for a cleared expression" verdict="unset"
"no_expression"
```

```json title="The reported code for a stored expression of a single zero" verdict="malformed"
"invalid_expression"
```

## Related rules

- Names: CRON-2
- Referenced by: CRON-2

---

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.