Human-Computer Interaction 3e Dix, Finlay, Abowd, Beale

exercises  -  7. design rules

EXERCISE 7.4

7.4 Can you think of any instances in which the 'noun-verb' guideline for operations, as suggested in the Apple human interface guidelines for the Desktop Interface, would be violated? Suggest other abstract guidelines or principles besides consistency which support your example. (Hint: Think about moving files around on the Desktop.)

answer

The noun-verb guideline suggests that we can view all operations that the user will perform as being composed of an action (the verb) acting with one argument (the noun). In the case of moving a file (or copying, for that matter), the action (move or copy) requires more than one argument. The way the move operation is performed requires the user first to select the icon for the file to be moved and then to indicate the move operation implicitly by dragging the selected icon to the destination folder. The nouns in this dialogue are the file to be moved and the destination folder. The verb is the move operation. The natural way to express this is in the order noun-verb-noun. Strictly speaking, in order to stick with the noun-verb guideline, we would have to indicate both the target file and the destination folder before indicating the move operation. That would be consistent, relative to input expression, with most other commands on the desktop. However, some principles of direct manipulation and familiarity to the user are more important. Moving files by dragging them on the desktop is very similar to the way we can pick up any object in the physical world and move it to its new location. And the dragging operation is incremental and easily recoverable; moving to one place can be undone within the same operation since the dragging can continue until the file is released.

The file-moving example is a slightly contrived one, because some could argue that there is no violation of the noun-verb guideline (hence, moving is still consistent with respect to input expression) because the verb is 'move to destination folder'. Perhaps a better example is a command to search a file system for files matching some specification. Here, the action is to do the qualified search and the argument or noun is the set of folders or volumes of the system that you want searched. Typically, this kind of operation is defined by some dialog box that allows the user to indicate in any order the specifics of the operation (the search parameters) and the folders or volumes to search. Once this unordered dialog is complete, the user then indicates that it is OK for the system to perform the operation. This kind of form-filling dialog subscribes to neither the noun-verb or verb-noun guideline; the order is more flexible for the user than consistent.


Other exercises in this chapter

ex.7.1 (ans), ex.7.2 (ans), ex.7.3 (open), ex.7.4 (ans), ex.7.5 (ans), ex.7.6 (ans), ex.7.7 (tut), ex.7.8 (tut), ex.7.9 (open)

all exercises for this chapter


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