---
title: "Facet"
description: "a proxy of the membership engine built by one procedure, with its four views"
section: concepts
address: /concepts/facet
contract: 0476e35e6e275db5
---

# Facet

a proxy of the membership engine built by one procedure, with its four views

[figure: Facet is a definition at follows scope. The drawing shows its fields and the objects that they point at.]

| property | value |
|---|---|
| kind | definition |
| scope | follows |
| key | the proxy it is |
| store | postgres |
| family | rules_engine |



## Fields


| field | type | required | note |
|---|---|---|---|
| `proxy` | `id` | yes |  |
| `seed` | `text` | yes |  |
| `candidates` | [FacetCandidate](/concepts/facetcandidate) | yes | each saying which way found it |
| `bar` | `number` | yes | in lift units, set from both sides: a room is kept when the lower bound of its share, over the seed's base rate, is at or over it; never under one, which is chance |
| `base_rate` | `share` | no | the share of everyone active in the window who is the seed's people: the chance a room's share is measured against |
| `negative_controls` | [ControlResult](/concepts/controlresult) | yes |  |
| `positive_controls` | [ControlResult](/concepts/controlresult) | yes |  |
| `gazetteer` | `id` | no | for a place facet |
| `scope` | [Scope](/concepts/scope) | yes | the scope the facet was built at and its memberships land in: shared for a buyers' facet that every tenant reads, built by the platform's own tenant; tenant for a tenant's own facet |



## Routes that use it
- [`/v1/work/build_facet`](/reference/work/build_facet) returns it