diff --git a/source/engine/mecanisms.js b/source/engine/mecanisms.js
index 9d31079ab..3cec78b91 100644
--- a/source/engine/mecanisms.js
+++ b/source/engine/mecanisms.js
@@ -3,6 +3,7 @@ import React from 'react'
 import {anyNull, val} from './traverse-common-functions'
 import {Node, Leaf} from './traverse-common-jsx'
 import {makeJsx, evaluateNode, rewriteNode, evaluateArray, evaluateArrayWithFilter, evaluateObject, parseObject, collectNodeMissing} from './evaluation'
+import {findRuleByName} from './rules'
 
 let constantNode = constant => ({nodeValue: constant, jsx:  nodeValue => <span className="value">{nodeValue}</span>})
 
@@ -609,6 +610,49 @@ export let mecanismComplement = (recurse,k,v) => {
 	}
 }
 
+export let mecanismSelection = (recurse,k,v) => {
+	if (v.composantes) { //mécanisme de composantes. Voir known-mecanisms.md/composantes
+		return decompose(recurse,k,v)
+	}
+
+	let dataSourceName = v['données']
+	let dataSearchField = v['dans']
+	let dataTargetName = v['renvoie']
+	let explanation = recurse(v['cherche'])
+
+	let evaluate = (situationGate, parsedRules, node) => {		
+		let collectMissing = node => collectNodeMissing(node.explanation),
+			explanation = evaluateNode(situationGate, parsedRules, node.explanation),
+			dataSource = findRuleByName(parsedRules, dataSourceName),
+			data = dataSource ? dataSource['data'] : null,
+			dataKey = explanation.nodeValue,
+			dataItems = (data && dataKey && dataSearchField) ? R.filter(item => item[dataSearchField] == dataKey, data) : null,
+			dataItemValues = dataItems ? R.values(dataItems) : null,
+			// TODO - over-specific! transform the JSON instead
+			dataItemSubValues = dataItemValues && dataItemValues[0][dataTargetName] ? dataItemValues[0][dataTargetName]["taux"] : null,
+			sortedSubValues = dataItemSubValues ? R.sortBy(pair => pair[0], R.toPairs(dataItemSubValues)) : null,
+			nodeValue = sortedSubValues ? Number.parseFloat(R.last(sortedSubValues)[1]) : null
+		return rewriteNode(node,nodeValue,explanation,collectMissing)
+	}
+
+	let jsx = (nodeValue, explanation) =>
+		<Node
+			classes="mecanism"
+			name="sélection"
+			value={nodeValue}
+			child={
+				explanation.category === 'variable' ? <div className="node">{makeJsx(explanation)}</div>
+				: makeJsx(explanation)
+			}
+		/>
+
+	return {
+		evaluate,
+		explanation,
+		jsx
+	}
+}
+
 export let mecanismError = (recurse,k,v) => {
 	throw "Le mécanisme '"+k+"' est inconnu !"+v
 }
diff --git a/source/engine/rules.js b/source/engine/rules.js
index a3bfdb8e3..04858bf36 100644
--- a/source/engine/rules.js
+++ b/source/engine/rules.js
@@ -68,7 +68,7 @@ export let disambiguateRuleReference = (allRules, {ns, name}, partialName) => {
 }
 
 // On enrichit la base de règles avec des propriétés dérivées de celles du YAML
-export let rules = rawRules.map(enrichRule, {taux_versement_transport})
+export let rules = rawRules.map(rule => enrichRule(rule, {taux_versement_transport}))
 
 
 /****************************************
diff --git a/source/engine/traverse.js b/source/engine/traverse.js
index ec595e73a..88762e651 100644
--- a/source/engine/traverse.js
+++ b/source/engine/traverse.js
@@ -8,7 +8,8 @@ import Grammar from './grammar.ne'
 import {Node, Leaf} from './traverse-common-jsx'
 import {
 	mecanismOneOf,mecanismAllOf,mecanismNumericalSwitch,mecanismSum,mecanismProduct,
-	mecanismScale,mecanismMax,mecanismMin, mecanismError, mecanismComplement
+	mecanismScale,mecanismMax,mecanismMin, mecanismError, mecanismComplement,
+	mecanismSelection
 } from "./mecanisms"
 import {evaluateNode, rewriteNode, collectNodeMissing, makeJsx} from './evaluation'
 
@@ -330,45 +331,6 @@ let treat = (rules, rule) => rawNode => {
 			{...parsedNode, evaluate: defaultEvaluate}
 }
 
-let mecanismSelection = (recurse,k,v) => {
-	let dataSourceName = v['données']
-	let dataSearchField = v['dans']
-	let dataTargetName = v['renvoie']
-	let explanation = recurse(v['cherche'])
-
-	let evaluate = (situationGate, parsedRules, node) => {		
-		let collectMissing = node => collectNodeMissing(node.explanation),
-			explanation = evaluateNode(situationGate, parsedRules, node.explanation),
-			dataSource = findRuleByName(parsedRules, dataSourceName),
-			data = dataSource ? dataSource['data'] : null,
-			dataKey = explanation.nodeValue,
-			dataItems = (data && dataKey && dataSearchField) ? R.filter(item => item[dataSearchField] == dataKey, data) : null,
-			dataItemValues = dataItems ? R.values(dataItems) : null,
-			// TODO - over-specific! transform the JSON instead
-			dataItemSubValues = dataItemValues ? dataItemValues[0][dataTargetName]["taux"] : null,
-			sortedSubValues = dataItemSubValues ? R.sortBy(pair => pair[0], R.toPairs(dataItemSubValues)) : null,
-			nodeValue = sortedSubValues ? Number.parseFloat(R.last(sortedSubValues)[1]) : null
-		return rewriteNode(node,nodeValue,explanation,collectMissing)
-	}
-
-	let jsx = (nodeValue, explanation) =>
-		<Node
-			classes="mecanism"
-			name="sélection"
-			value={nodeValue}
-			child={
-				explanation.category === 'variable' ? <div className="node">{makeJsx(explanation)}</div>
-				: makeJsx(explanation)
-			}
-		/>
-
-	return {
-		evaluate,
-		explanation,
-		jsx
-	}
-}
-
 //TODO c'est moche :
 export let computeRuleValue = (formuleValue, condValue) =>
 	condValue === undefined