I’ve been studying usability evaluation methods (UEMs), which although not directly related to taxonomy work, are relevant for anyone involved in information architecture (IA). I was surprised at how controversial a subject usability is, having assumed that everyone wants their sites to be as usable as possible. However, assessing usability does involve a lot of judgement calls and tradeoffs, which is one reason why some people seem to take against it.
You have to decide who you are going to focus your usability testing on, perhaps choosing a “core user group” rather than trying to please everybody. You have to decide what aspects of usability you are going to focus on – for example accessibility (everybody should be following minimum W3C standards anyway), but you might legitimately decide that you are not going to worry about making your site easy for children to read (e.g. if it is a postgraduate discussion forum). Then you need to decide if you are going to try to make individual tasks as efficient as possible (e.g. not using as many keystrokes) or look at the site as a whole (e.g. a social networking site might place a higher value on being fun and funky over being efficient to use).
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