class RdfEngine implements Engine {

    @Override
    public Set<User> getUsers() {
        Set<User> users = new HashSet<>();
        try (RepositoryConnection conn = repository.getConnection()) {
            GraphQuery query = conn.prepareGraphQuery(GET_USERS_QUERY);
            Model usersModel = QueryResults.asModel(query.evaluate(), mf);
            users.addAll(userFactory.getAllExisting(usersModel));
        }
        return users;
    }

}