public boolean isRelation()
    {
        if (getType() == TYPE_SEQUENCE)
            {
            return true;
            }
        if (getType() == TYPE_BAG)
            {
            return true;
            }
        if (getType() != TYPE_SET)
            {
            return false;
            }
        if ((m_setType != null) && (m_setType.getType() != TYPE_TUPLE))
            {
            return false;
            }
        if ((m_setType != null) && (m_setType.m_tupleTypes.size() != 2))
            {
            return false;
            }
        return true;
    }