+                                       ->arrayNode('facebook')
+                                               ->addDefaultsIfNotSet()
+                                               ->children()
+                                                       ->arrayNode('apps')
+                                                               ->treatNullLike([])
+                                                               ->defaultValue($defaults['facebook']['apps'])
+                                                               ->scalarPrototype()->end()
+                                                       ->end()
+                                                       ->integerNode('height')->min(0)->defaultValue($defaults['facebook']['height'])->end()
+                                                       ->integerNode('width')->min(0)->defaultValue($defaults['facebook']['width'])->end()
+                                               ->end()
+                                       ->end()
+                                       ->scalarNode('locale')->cannotBeEmpty()->defaultValue($defaults['locale'])->end()
+                                       ->scalarNode('locales')->cannotBeEmpty()->defaultValue($defaults['locales'])->end()
+                                       ->scalarNode('languages')->cannotBeEmpty()->defaultValue($defaults['languages'])->end()
+                                       ->arrayNode('path')
+                                               ->addDefaultsIfNotSet()
+                                               ->children()
+                                                       ->scalarNode('cache')->defaultValue($defaults['path']['cache'])->end()
+                                                       ->scalarNode('public')->defaultValue($defaults['path']['public'])->end()
+                                               ->end()
+                                       ->end()