<spreadsheet>
  <worksheet name="Student">
    <column index="0" name="id"/>
  	<column index="1" name="firstname"/>
  	<column index="2" name="lastname"/>
    <column index="3" name="age" datatype="integer"/>
    <column index="4" name="supervisor"/>
    <column index="5" name="modules" many="true"/>
  </worksheet>
  <worksheet name="Mark">
    <column index="0" name="student"/>
    <column index="1" name="module"/>    
    <column index="2" name="mark" datatype="integer"/>
  </worksheet>
  <worksheet name="Staff">
    <column index="0" name="id"/>
  	<column index="1" name="firstname"/>
  	<column index="2" name="lastname"/>
    <column index="3" name="teaches" many="true" delimiter=","/>
  </worksheet>
  <worksheet name="Module">
  	<column index="0" name="id"/>
  	<column index="1" name="title"/>
  	<column index="2" name="term"/>
  </worksheet>
  <reference source="Student->supervisor"
             target="Staff->id"/>
  <reference source="Student->modules"
             target="Module->id"/>           
  <reference source="Staff->teaches"
             target="Module->id"/>
  <reference source="Mark->module"
             target="Module->id"/>
  <reference source="Mark->student"
             target="Student->id"/>                      
</spreadsheet>