protected function _merge(array $data, array $item) {
		if (!isset($item['id'])) {
			return $data;
		}
		$id = $item['id'];

		$defaults = [
			'ids' => [],
			'translated' => null,
			'flags' => [],
			'comments' => [],
			'occurrences' => []
		];
		$item += $defaults;

		if (isset($item['context']) && $item['context']) {
			$id .= '|' . $item['context'];
		}

		if (!isset($data[$id])) {
			$data[$id] = $item;
			return $data;
		}
		foreach (['ids', 'flags', 'comments', 'occurrences'] as $field) {
			$data[$id][$field] = array_merge($data[$id][$field], $item[$field]);
		}
		if (!isset($data[$id]['translated'])) {
			$data[$id]['translated'] = $item['translated'];
		} elseif (is_array($item['translated'])) {
			$data[$id]['translated'] = (array) $data[$id]['translated'] + $item['translated'];
		}
		return $data;
	}