<?xml version="1.0" encoding="UTF-8"?>
<model>
  <entity name="heartbeat-report" root="true">
    <attribute name="domain" value-type="String" key="true"/>
    <attribute name="startTime" value-type="Date" format="yyyy-MM-dd HH:mm:ss" />
    <attribute name="endTime" value-type="Date" format="yyyy-MM-dd HH:mm:ss" />
    <entity-ref name="machine" type="map" names="machines" />
  </entity>
  <entity name="machine">
    <attribute name="ip" value-type="String" key="true"/>
    <entity-ref name="period" type="list" names="periods" />
  </entity>
  <entity name="period">
  </entity>
 </model>