---
title: NF X50-151
lang: en
type: notion
tags:
  - proj
  - notion
  - stub
prerequis: []
aa: []
draft: false
source_fr: conduite/proj/afnor-nfx50-151.md
source_sha256: aeac6f11bbb73f7fa06807fa3546695d23fc314d580bd5410d0aebb0f7ab967b
---

The **NF X50-151 standard** is the French AFNOR standard that defines the framework for the functional analysis of a product or a system. It governs the functional expression of need — carried out in practice by the [[bete-a-cornes-en|bête à cornes]] and the [[pieuvre-en|pieuvre]], both from the APTE method — and requires functions to be characterised by figures, through the **criterion / level / flexibility** triplet.

> [!info] Getting the standard
> The official standard is **not free**: it is sold on the AFNOR website. For a first educational look, see the article [Analyse fonctionnelle (conception) on Wikipedia](https://fr.wikipedia.org/wiki/Analyse_fonctionnelle_(conception)).