A system/application that does not exist as one giant program. This can mean multiple processes on the same machine to servers on multiple machines miles apart. Doing this requires communication between the various parts of the system. The communication can be achieved in many ways:

• CORBA
• DCE
• DCOM
• EJB
• RPC (remote procedure call)
• Shared memory based interaction
• Named Pipe communication
• Socket level programming
• Message Queuing
• Other IPC (inter-process communication) mechanisms
• Database tables, triggers and polling