---
title: "BackfillInput"
description: "a source, an access method, a window and a plane; the platform fills the reading, so the same request over a catalogue read again is new work"
section: concepts
address: /concepts/backfillinput
contract: 0476e35e6e275db5
---

# BackfillInput

a source, an access method, a window and a plane; the platform fills the reading, so the same request over a catalogue read again is new work

[figure: BackfillInput is a value at none scope. The drawing shows its fields and the objects that they point at.]

| property | value |
|---|---|
| kind | value |
| scope | none |
| key | none |
| store | none |
| family | harness |



## Fields


| field | type | required | note |
|---|---|---|---|
| `source` | `id` | yes |  |
| `access_method` | `id` | yes |  |
| `window` | [Window](/concepts/window) | yes |  |
| `plane` | [Plane](/concepts/plane) | yes |  |
| `reading` | `text` | no | the hash of the procedure reading the backfill runs over, filled by the platform from the newest reading of the source through the way's connector; a caller leaves it empty |



## Routes that use it
- [`/v1/work/backfill`](/reference/work/backfill) takes it as input