Selection techniques for input in rehabilitation computing.

Not finished yet. Give me time .......

Selection is the basis of ( almost ? ) all computer input as used in communication devices, because it is always necessary to use some action we can perform to select which letter, or word, or sentence, or picture, or sound, or whatever is to be printed, or displayed, or spoken, or whatever next. Whether we use a keyboard or a mouse or some special input device, in one way or another we ( almost ? ) always use it to select something, or some things, from a collection of other possibilities.

The repeated "almost" is just to play safe. If you think of an exception, please tell me.

It is generally accepted that there are three sorts of selection :

Direct selection : A set of items is offered, and one is chosen by something amounting to pointing at it. Examples include pressing a key on a keyboard, or selecting an icon with a mouse pointer. Direct selection methods often require a reasonable degree of agility.
Scanning : Items are offered one by one, and an item is selected if some defined action is taken while it is on offer. Some GUIs provide scanning by operation of ( say ) the tabulation key, which highlights various screen items in turn, and you can do something else ( press Return ) to select an item when it's highlit. This method is used in many rehabilitation interfaces, because you only need one switch to do it.
Encoding : The action you use to make the selection is not obviously related to the result of the selection, and you have to remember a code of some sort to make it work. The use of control keys and function keys is an example. Encoding is usually used in such a way that a short sequence of actions returns a much bigger result - so a code of a few letters might retrieve a whole sentence from a database. This method can be very effective if it works, but is cognitively comparatively demanding, in that you have to remember the codes.

It isn't always easy to categorise interface designs in these terms - is selection from a menu by entering the item number direct selection ( all the menu is displayed, and the number is equivalent to pointing ) or encoding ( the number entered isn't in fact the item selected ) ? - but the categories do identify clearly distinct methods, and emphasise that there is a choice.

The topic of selection is important in rehabilitation systems because many people with various sorts of disability find it hard to do. If you can only move slowly, or jerkily, or if you can only control the muscles above your neck, or if you can't see a display, then the common means of selection might not be readily accessible to you. Even if they are accessible, using them might be excruciatingly slow. The design and implementation of good selection methods is therefore a significant topic in rehabilitation computing.

WORKING NOTES : AC91 ( The multiple-key idea ); AC98 ( The multiple-key implementation ); AC108 ( Detecting multiple key depressions ); AC109 ( Operating instructions ); AC110 ( preliminary results ).

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