|
|
Masakatsu Sugimoto*, Kimiyo Takahashi**
A conventional keyboard is not suited for mobile devices. Touch typing on conventional keyboard requires both hands operation. It is not suited for mobile environments: when a user is in standing position, while he or she is walking, while he or she is in a car, etc.[3], [4].
"Castanets operation" is shown in Figure 1. One is holding a card with the thumb and a part of his palm. On the card there are keys for text input and a stick and switches for mouse data input. One can input text and mouse data with the other four fingers: the index finger, the middle finger, the ring finger and the little finger. Thus one is able to operate a mobile device using only one hand.
© Copyright on this material is held by the authors
Each row has six keys. At the home position row, the index finger covers a home position key and a key to the left of the home position key. A little finger covers two keys: the home position key and a key to the right of it. Other two fingers: the middle finger and the ring finger covers only one key each. For the upper row and the lower row, same is applied as for the home position row.
Next step is to divide these eighteen keys into keys for alphabetic characters input and keys for control. Fourteen keys among the eighteen keys are for alphabetic characters. If we would assign one key for an alphabetic character, we would have twelve key less in the card, because twenty six alphabetic characters are needed for English text. So our key assignment scheme is as follows; two alphabetic characters for a key for twelve keys and one alphabetic character for a key for the remaining two keys.
The actual assignment of each of the alphabetic characters to the keys was done according to the frequency of appearance of each alphabetic character in ordinary English text, for easiness of fingers' movement[1].
We have adopted quite a new scheme. No selection operation needed when a user push a key for which two alphabetic characters are assigned. We will apply an ambiguity resolution logic, word by word. That is, after a user types a string of alphabetic characters which consists of a word, he will push a control key: AR-key. AR means ambiguity resolution. At this moment, some characters in the string have ambiguity, because the user hasn't specify which one of two alternatives he intends to input.
The AR-key is pushed by the little finger at its home position, for typing convenience. When the key is pushed, the ambiguity resolution logic will retrieve a set of words which the logic infers that the user might have intended to, by the input string. The set will be accessed through internal word dictionaries and rules for English words. Then the set of words are displayed on a screen. Interactively, the user selects what word he intends to input among the set. He will use the AR-key again, for this selection process, for input convenience.
The ambiguity resolution logic is realized in the SHK support software[2], [5].
The support software is working on MS Windows.
We start gathering data on typing speed. We are sure that an experienced user will be typing more that forty words per minute.
By combining advances in microprocessors and display units for mobile devices with SHK cards, we will be able to attain very powerful information and communication media which we will use in everyday life, anytime, anywhere.