Lattices of size 3

<structure name="Lat_3_1" size="3">
  <element name="0" x="0" y="0"/>
  <element name="1" x="0" y="1"/>
  <element name="2" x="0" y="2"/>
  <relation name="uppercovers" arity="2" type="list">
    <set id="0"> 1 </set>
    <set id="1"> 2 </set>
    <set id="2"> </set>
  </relation>
</structure>