[syslog-ng] More then one application on same server

Hi, I have more then one applications running on my server which generates and sends logs to central server using syslog-ng, and I need to identify in the syslog that which log is coming from which application?? currently I can only identify the server name (as the source of orginating all logs) which mix all the logs. Can anybody please help me in solving my issue?? I am kind of stuck at this point. I will be thankful for any kind of help. B.R. Ash.