Tuesday, November 27, 2007

Fit for purpose

People rarely build a database system just for fun: they have a goal in mind, usually related to the data for which the database will form the receptacle. They will, therefore, need to consider always their objective(s) to ensure that the system they are building is fit for purpose.

It seems, however, that human nature often makes people concentrate on the process rather than the objective, and in the data world this directly affects data quality. I often come across companies and individuals who, when deciding between software A, which is slower but produces good quality data, and software B, which is faster but produces poor quality data, plump for software B because they have lost sight of the objective and are considering the process.

I often use the example of the Brussels underground system. The trains kept a strict timetable, which meant that each one would only stop at each station for a fixed number of seconds. The number of seconds did not appear to differ according to the volume of passengers at that station. As a result, the doors would close and trains would move off before all the passengers had had a chance to get on and off. Regular passengers knew about this, so when stepping onto the train would then simply stop where they were because they had to be in a position to get off again quickly, blocking the entrance and exit. At busy stations a scrum ensued as everybody tried to get on and off at the same time. Many a morning I had to walk to work from the stop after the one I had wanted because I hadn't managed to fight my way out in time.

Clearly, the transport company was concentrating on its process - sticking to its timetable - rather than its objective of moving passengers to where they needed to be.

I was reminded of this when I recently read of Amsterdam trams playing the same tricks. Some were whizzing past stops because they needed to stick to a timetable. Compounding this was the fact that the city of Amsterdam fine the tram company for each late running tram. Clearly nobody had thought this through properly - the city was basing its assessment of the tram company on the process rather than the objective. The tram company would be better off running all its trams without passengers and therefore avoiding fines, but that's hardly fit for purpose.


(c) 2007 Graham Rhind. Reproduction only allowed with permission. Comment and dialogue welcome.

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