I am working on a project to integrate SFDC Cases into a backend system.  To integrate the 2, the backend system has a listener that captures outbound messages from the Case object (and 3 related custom objects), and uses that soap data to update the case in that system.  All is good.

We are now ready to roll out the solution, and are told that users need to be able to delete records (like Cases) in SFDC, and have that delete occur in the backend system as well.  So we are using a before delete trigger in SFDC to send a SOAP message to the external system to delete the record there, and then the delete occurs in SFDC. 

The thing is, since the listener is already set up in the external system, all I want to do is send a SOAP message in the same format as an outbound message to the external system with a certain value that will result in the deletion there.  (For example, Case.Mark_for_Delete__c = -1).  So really, in the external system, it is just an update, so that same format will work fine.

My question is:  what is the <Id> field under the <Notification> node in the outbound message?  I am making the apex that generates the SOAP message as dynamic as possible, so that we can migrate from sandbox to QA, to PD, so I want all values that change from instance to instance to be dynamic, but I can't figure out where the value of that ID comes from.  I get the <OrganizationId>, and the <Id> of the object (for the record), but don't know what the Notification Id is.

Pleaes help!!!