# `data.lifecycle_section`

Lifecycle has a section it doesn't take, or lacks one it needs.

Area 5, [Data](../topics/data.md); not declinable; the next step is usually the agent's.

A lifecycle holds `visible:`, `initial:`, `transitions:` and `purge:`, each once; a transition holds `when:` and `set:`, and `purge:` holds `after:` and `since:`:

```jadpo
entity Todo {
    id: Uuid
    deleted_at: Instant?

    lifecycle: {
        visible: deleted_at == none
        hidden: deleted_at != none
    }
}
```

```text
error: `hidden` isn't part of a lifecycle
 --> main.jadpo:7:9
  |
7 |         hidden: deleted_at != none
  |         ^^^^^^ not a section here
  reason: A lifecycle holds `visible:`, `initial:`, `transitions:` and `purge:`.
  next: Remove `hidden` from the lifecycle (agent)
  rule: data.lifecycle_section
  help: https://jadpo.dev/docs/errors/data.lifecycle_section

check failed: 1 error, 1 file
```