Handwriting as computer interface.

I. Guyon and C. Warwick.
In Survey of the State of the Art in Human Language Technology. NSF.

``Pen computers'' offer an interesting alternative to paper. One can write directly on a LDC (Liquid Crystal Display) screen with a stylus or ``pen''. The screen has an invisible sensitive matrix which records the position of the pen on the surface. The trajectory of the pen appears almost instantaneously on the screen giving the illusion of ink (``electronic ink''). Handwriting recognition allows text and computer commands to be entered.

While nothing opposes the idea of a computer that would use multiple input modalities including speech, keyboard and pen, some applications call for a pen-only computer interface: in a social environment, speech does not provide enough privacy; for small hand-held devices and for large alphabet (e. g. Chinese), the keyboard is cumbersome. Applications are numerous: personal organizer, personal communicator, notebook, data acquisition device for order entries, inspections, inventories, surveys, etc.

The dream is to have a computer that looks like paper, feels like paper but is better than paper. Currently, paper is the most popular medium for sketching, note taking and form filling, because it offers a unique combination of features: light, cheap, reliable, available almost everywhere any time, easy to use, flexible, foldable, pleasing to the eye and to the touch, silent. But paper has also its drawbacks: in large quantities it is no longer light and cheap, it is hard to reuse and recycle, difficult to edit, expensive to copy and to mail, inefficient to transform into computer files. With rapid technology progress, electronic ink could become cheaper and more convenient than paper, if only handwriting recognition worked!

As of today, the mediocre quality of handwriting recognition has been a major obstacle to the success of pen computers. Users report that it is ``too inaccurate, too slow and too demanding for user attention'' . The entire pen computing industry is turning its back on handwriting and reverting to ``popup keyboards''. On small surfaces, keypad tapping is difficults and slow: 10-21 words per minute, compared to 15-18 wpm for handprint and 20-32 wpm for a full touch screen keyboard. However, it remains the preferred entry mode because of its low error rate: less than 1 percent for the speed quoted, compared to 5-6 percent with a state-of-the-art recognizer (CIC). In one of our recent studies, we discovered that a good typist tolerates only up to 1 percent error using a special keyboard that introduced random typing errors at a software-controllable rate; 0.5 percent error is unnoticeable; 2 percent error is intolerable! Human subjects make 4-8 percent error for isolated letters read in the absence of context and 1.5 percent error with the context of the neighboring letters. Therefore, the task of designing usable handwriting recognizers for pen computing applications is tremendously hard. Human recognition rates must be reached and even outperformed.

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