Think! Interactive Systems Need Safety Locks

Harold Thimbleby


This paper uses a simple analogy. A gun is designed to shoot bullets, but it is obvious that accidentally shooting is a danger one should avoid if at all possible. Thus guns have safety locks, which aim to protect users and bystanders.
Interactive computer systems sometimes accidentally do bad things too, but something like "safety locks" are not often enough implemented to help protect user or bystanders from harm.
Worse, user interfaces often behave quite unpredictably with erroneous input - rather than blocking errors and requiring the user to correct them. This is a bit like guns that misbehave.
Computers and computers embedded in everyday devices are not always as dangerous as guns, although there are many cases where they can be as dangerous. Medical devices may give patients undetected overdoses. In-car entertainment devices, like radios, may, through their badly-designed user interfaces, cause a driver to have an accident. A slip in a spreadsheet may be the first step towards an organisation going bankrupt. And so on.
The solution should include better design, including the concept of safety locks, that block some forms of user error.


safety locks; human error; number entry; user interface design

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