Transport Route Planner Journey Planner How Can I Write A Route Planner Based On Public Transport Networks?

How can I write a route planner based on public transport networks? - transport route planner journey planner

I'm for building a travel planner journeyplanner.org like my hometown interested, but you do not know where to start. The program must be able to generate a route on a fast track and, with the introduction of the user is not who wants to - then, and they instruct on the shorter path through the computation itself. Which program should I use to do this? How can the rules of the transportation system? Should I start with a database / MySQL? Any help is greatly appreciated