Train Ticket reservation system is a very complicated system. It is complicated because it consists of more number of entities and processes. Data in this system should be collected from more number of entities and need to be processed within more number of processes. Example of this type of system is explained on the link below
This Train Ticket Reservation System consists of four external entities; namely Customer,Vendor, Schedule manager and Train representative. Customer are the one who issue for the tickets, Vendor are the counterman who receives payment to handover tickets to the customer, Schedule manager manages the time schedules of train with accordance to the route and Train Representative monitors the overall activities on the system like the seats capability and passenger facility. These four entities are governed by the single or multiple processes through the flow of data.
This Data Flow Diagram was taken directly from my notes so if you have any problems in understanding it, you are kindly requested to leave comment below.
The standard of naming process-name is; process name should be action verb that specifies the operation(see on: How do we begin to construct Data Flow Diagrams? ). Advantage of preparing this DFD can be; proper knowledge of Data flow, effects of external entities in the system, determination of process in the overall system.