pgRouting extends the PostGIS / PostgreSQL geospatial database to provide geospatial routing functionality. Advantages of the database routing approach are:
Data and attributes can be modified by many clients, like Quantum GIS and uDig through JDBC, ODBC, or directly using Pl/pgSQL. The clients can either be PCs or mobile devices.
Data changes can be reflected instantaneously through the routing engine. There is no need for precalculation.
The “cost” parameter can be dynamically calculated through SQL and its value can come from multiple fields or tables.