Human-Computer Interaction 3e Dix, Finlay, Abowd, Beale
Imagine a normal calculator except that it displays A for 0, B for 1, up to J for 9. So the number 372 would appear as DHC. Does this affect the formal transparency of the calculator? Should it?
Formally, this would not affect the transparency property of a calculator. Any function from display to effect that held for the numbers would also hold for their alphabetic counterparts by just composing it with the code A for 0, B for 1, up to J for 9. Of course, most people would probably find the encoded calculator quite a bit more difficult to use than one that used the normal ten digits. The important lesson here is that the formal expression of the transparency property does not indicate how difficult it is for a human to determine the function between display and effect. The formal expression just requires that there be some function. In practice, human users would probably judge the encoded calculator as unpredictable (that is, not transparent). The moral is that even though we can capture a usability property formally this does not mean that we have captured the entire intent of the property. The transparency property would have to be augmented in order to measure the complexity, from the user's perspective, of the function between display and effect.
Other exercises in this chapter
ex.17.1 (ans), ex.17.2 (ans), ex.17.3 (ans), ex.17.4 (ans), ex.17.5 (tut), ex.17.6 (tut), ex.17.7 (tut), ex.17.8 (tut), ex.17.9 (tut)
all exercises for this chapter