protected function subjectsAndPredicatesOfChangeUrisToAliases(array $subjectsAndPredicatesOfChange)
    {
        $aliases = array();
        foreach($subjectsAndPredicatesOfChange as $subject=>$predicates)
        {
            $subjectAlias = $this->labeller->uri_to_alias($subject);
            $aliases[$subjectAlias] = array();
            foreach($predicates as $predicate)
            {
                $aliases[$subjectAlias][] = $this->labeller->uri_to_alias($predicate);
            }
        }
        return $aliases;
    }