Monday, 16 March 2009

Multicriteria Decision Making

A great deal is being written in O.R. journals and related publications about the science of multiple criteria decision making (MCDM). A few days ago I experienced one of the ways that MCDM can be especially complex.

I regularly visit a university to examine the undergraduate scripts and attend meetings as part of my duties as external examiner. My hosts book me a hotel for my overnight stay. Up to now, they have booked me into one of two hotels, E and I. I have been indifferent between them.

Both are a few minutes' walk from a railway station. Both are a few minutes' walk from the offices where we meet. Both have all the facilities of a modern impersonal hotel. Both have a good breakfast bar. E is close to a nice place to eat in the evening. I has its own in-house restaurant. I have been content in each one.

But earlier this month, I was booked into a third hotel, H. H is much further from the station and the office. Being concerned for the planet, I don't want to take a taxi for a journey that takes 20 to 25 minutes on foot, so I walk. H has all the facilities of E and I, and there was a very pleasant place for an evening meal close by.

But on the criteria that I had judged E and I by, H would be less attractive. But H has a swimming pool that is large enough to have a "decent" swim. E and I do not. A new dimension has been added to the MCDM problem. And that makes the choice for me more complex. Where shall I ask to stay next time?

Of course, if I took taxis everywhere, there would be no problem. But I do not. And there's the problem of weighing the advantages of convenience against the joy of a swimming pool. No wonder MCDM is challenging!

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