-                                                       ->arrayNode('config')
-                                                               ->isRequired()
-                                                               ->addDefaultsIfNotSet()
-                                                               ->children()
-                                                                       ->scalarNode('prefix')->isRequired()->defaultValue($defaults['config']['prefix'])->end()
-                                                                       ->scalarNode('scheme')->isRequired()->defaultValue($defaults['config']['scheme'])->end()
-                                                                       ->integerNode('timeout')->isRequired()->min(0)->defaultValue($defaults['config']['timeout'])->end()
-                                                                       ->scalarNode('agent')->isRequired()->defaultValue($defaults['config']['agent'])->end()
-                                                                       ->integerNode('redirect')->isRequired()->min(1)->defaultValue($defaults['config']['redirect'])->end()
-                                                               ->end()
-                                                       ->end()
-                                                       ->arrayNode('output')
-                                                               ->isRequired()
-                                                               ->addDefaultsIfNotSet()
-                                                               ->children()
-                                                                       ->scalarNode('css')->isRequired()->defaultValue($defaults['output']['css'])->end()
-                                                                       ->scalarNode('js')->isRequired()->defaultValue($defaults['output']['js'])->end()
-                                                                       ->scalarNode('img')->isRequired()->defaultValue($defaults['output']['img'])->end()
+                                                       ->scalarNode('name')->cannotBeEmpty()->defaultValue($defaults['config']['name'])->end()
+                                                       ->scalarNode('scheme')->cannotBeEmpty()->defaultValue($defaults['config']['scheme'])->end()
+                                                       ->integerNode('timeout')->min(0)->max(300)->defaultValue($defaults['config']['timeout'])->end()
+                                                       ->scalarNode('agent')->cannotBeEmpty()->defaultValue($defaults['config']['agent'])->end()
+                                                       ->integerNode('redirect')->min(1)->max(30)->defaultValue($defaults['config']['redirect'])->end()
+                                               ->end()
+                                       ->end()
+                                       ->arrayNode('output')
+                                               ->addDefaultsIfNotSet()
+                                               ->children()
+                                                       ->scalarNode('css')->cannotBeEmpty()->defaultValue($defaults['output']['css'])->end()
+                                                       ->scalarNode('js')->cannotBeEmpty()->defaultValue($defaults['output']['js'])->end()
+                                                       ->scalarNode('img')->cannotBeEmpty()->defaultValue($defaults['output']['img'])->end()
+                                               ->end()
+                                       ->end()
+                                       ->arrayNode('filters')
+                                               ->addDefaultsIfNotSet()
+                                               ->children()
+                                                       ->arrayNode('css')
+                                                               /**
+                                                                * Undocumented
+                                                                *
+                                                                * @see Symfony/Component/Config/Definition/Builder/ArrayNodeDefinition.php +513
+                                                                */
+                                                               ->addDefaultChildrenIfNoneSet()
+                                                               ->arrayPrototype()
+                                                                       ->children()
+                                                                               ->scalarNode('class')
+                                                                                       ->isRequired()
+                                                                                       ->cannotBeEmpty()
+                                                                                       ->defaultValue($defaults['filters']['css'][0]['class'])
+                                                                               ->end()
+                                                                               ->arrayNode('args')
+                                                                                       //->isRequired()
+                                                                                       ->treatNullLike([])
+                                                                                       ->defaultValue($defaults['filters']['css'][0]['args'])
+                                                                                       ->scalarPrototype()->end()
+                                                                               ->end()
+                                                                       ->end()