Response:

<?xml version="1.0" encoding="UTF-8"?>

<user>

  <created-at type="datetime">2010-06-02T04:15:49Z</created-at>

  <creation-group-left type="integer">1</creation-group-left>

  <id>3</id>

  <email>mat_aki@example.com</email>

  <updated-at type="datetime">2010-09-07T04:39:07Z</updated-at>

  <participations type="array">

    <participation>

      <admin type="boolean">true</admin>

      <created-at type="datetime">2010-06-02T04:15:51Z</created-at>

      <id type="integer">286</id>

      <name>mat_aki</name>

      <updated-at type="datetime">2010-09-07T04:41:17Z</updated-at>

      <group>

        <created-at type="datetime">2010-06-02T04:15:49Z</created-at>

        <name>My room1</name>

        <updated-at type="datetime">2010-09-07T04:41:17Z</updated-at>

        <to-param>61</to-param>

      </group>

    </participation>

    ...

  </participations>

</user>