SAP EM XML - Understanding the EPCIS message for the PTA scenario

<EPCISBody>
 <EventList>
  <ObjectEvent>    <== OBJECTEVENT is the external event code / unexpected event
   <eventTime>2008-10-09T12:05:48-07:00</eventTime>
   <eventTimeZoneOffset>-07:00</eventTimeZoneOffset>
   <epcList>
     <epc>urn:epc:id:sgtin:0037000.103015.30066</epc>
   </epcList>
   <action>OBSERVE</action>   <== Event message Extension - Field ACTION - mapped to parameters
   <bizStep>urn:epcglobal:fmcg:bizstep:shipped</bizStep> <== Event message Extension - Field BIZSTEP
   <disposition>urn:epcglobal:hls:disp:active</disposition> <== Event message Extension - Field DISPOSITION
   <readPoint> <== Event message Extension - Field READPOINT
     <id>urn:epcglobal:fmcg:loc:0000000001000.APCI_SHIP</id>
   </readPoint>
   <bizLocation> <== Event message Extension - Field BIZLOCATION
     <id>urn:epcglobal:fmcg:loc:0000000001000.1</id>
   </bizLocation>
   <extension>
     <SAPEPCExtension>   <== EH Header Extension
       <EPC>urn:epc:id:sgtin:0037000.103015.30066</EPC>
       <NameValuePair>
          <ParameterName>PRODUCT</ParameterName> <== EH Header Extension - Field PRODUCT
          <ParameterValue>35121451</ParameterValue>
       </NameValuePair>
       <NameValuePair>
         <ParameterName>GTIN</ParameterName> <== EH Header Extension - Field GTIN
         <ParameterValue>10037000030154</ParameterValue>
       </NameValuePair>
       <NameValuePair>
         <ParameterName>BATCH_ID</ParameterName> <== EH Header Extension - Field BATCH_ID
         <ParameterValue>ABCD1237</ParameterValue>
       </NameValuePair>
     </SAPEPCExtension>
   </extension>
 </ObjectEvent>
</EventList>
</EPCISBody>
</n0:EPCISDocument>