<xmi>
  <row name="element1" level0="0" level1="0"/>
  <row name="element2" level0="0" level1="0"/>
  <row name="element3" level0="1" level1="0"/>
  <row name="element4" level0="1" level1="1"/>
  <row name="element5" level0="1" level1="1"/>
  <row name="element6" level0="1" level1="1"/>
</xmi>

<xmi>
  <document>
    <node id="0">
      <node id="0">
        <leaf name="element1">
        <leaf name="element2">
      </node>
    </node>
    <node id="1">
      <node id="0">
        <leaf name="element3">
      </node>
      <node id="1">
        <leaf name="element4">
        <leaf name="element5">
        <leaf name="element6">
      </node>
    </node>
  </document>
</xmi>

module RowsToDocument;
create OUT : OUTMM from IN : INMM;

rule Leaf {
  from
    row : INMM!Row
  to
    node : OUTMM!Leaf (
      name <- row.name
    )
}

unique lazy rule Level0Node {
  from
    level0 : Integer
  to
    node : OUTMM!Node (
      id <- level0,
      children <- INMM!Row.allInstances()
        ->collect(r -> r.level1)->asSet()
        ->collect(level1 -> thisModule.Level1Node(level0, level1))
    )
}

unique lazy rule Level1Node {
  from
    level0 : Integer,
    level1 : Integer
  to
    node : OUTMM!Node (
      id <- level1,
      children <- INMM!Row.allInstances()
        ->select(r -> r.level0 = level0 and r.level1 = level1)
    )
}

endpoint rule Document() {
  to
    document : OUTMM!Document (
      children <- INMM!Row.allInstances()
        ->collect(r -> r.level0)->asSet()
        ->collect(level0 -> thisModule.Level0Node(level0))
    )
}