Mostly I have been vacillating about which case study to use - I have so many part-finished projects. At first I revived the Whisky project, but after a lot of work, this felt like a bit of a slog - it was good as a modeling exercise but didn't reveal the power of XML and XQuery to my satisfaction. I then switched to the Bus Timetable project, which is much more realistic and one which I want to solve to replace the existing PHP/MySQL application with its hand-crafted timetables. However the data here is very complex, and the data files I have so far are incomplete. Nevertheless, this is the case study I settled on, although I did a short detour into the DVD hire example and of course there is always StudentsOnline, the main site we are developing with this technology.
Timetables come from TravelLine South-West in the form of TransXChange files. These first need processing to a more amenable structure. The actual data model is highly interlinked which makes for some XPath fun. Conversion is required to calculate absolute times (TXC has time differences between stops) and to convert from OS Easting and Northing to Lat/Long . With the simplified structures, I can present the data in various ways. HTML pages show the stops and the departures times but the neat idea is to generate kml files to overlay on Google Earth. Using a NetworkLink, I can display changing times on the map. The XPath date and time functions are a great help.
Other bits of functionality include an Ajaxian incremental Bus stop locator and membership registration rretainig favourite stops and services.
Here are some useful links for this project:
- eXist database home
- an XQuery tutorial from Howard Katz
- A basic Timetable implementation (pending)
- TransXChange documentation
- TravelLine South West
- Google Earth
- kml description and reference
