ref="manual_3.html#Concepts">3.2 Concepts</a></li>
    <li><a name="toc-Relations-1" href="manual_3.html#Relations">3.3 Relations</a></li>
    <li><a name="toc-Relation-Hierarchies-1" href="manual_3.html#Relation-Hierarchies">3.4 Relation Hierarchies</a></li>
    <li><a name="toc-Functions-1" href="manual_3.html#Functions">3.5 Functions</a></li>
    <li><a name="toc-Defined-Concepts-1" href="manual_3.html#Defined-Concepts">3.6 Defined Concepts</a></li>
    <li><a name="toc-Negation-and-Open-and-Closed-World