[Erp5-users] erp5 callback functionality

[Peter Burgheim-Losse]

Dear erp5 list members,

to implement an ERP system into the infrastructure of a midsize company 
I would like to use erp5 but the following functionality is needed:

scenario:
A message is sent to erp5 containing a query or an order. This query is 
then accepted/rejected by a staff member. Now erp5 has to send a message 
containing this status change to an external system or somehow trigger 
this system to send a status request to erp5.

1) Is erp5 able to send messages to external systems?
2) Is there a trigger function at
    2.1) database layer?
    2.2) process layer?

Thanks a lot in advance for your feedback or a reference to erp5's 
documentation.

Kind regards
Peter