Interlaced QWERTY - Accommodating ease of visual search and input flexibility in shape writing

Shape writing is an input technology for touch-screen mobile phones and pen-tablets. To shape write text, the user spells out word patterns by sliding a finger or stylus over a graphical keyboard. The user's trace is then recognized by a pattern recognizer. In this paper we analyze and evaluate various keyboard layouts, including alphabetic, optimized (ATOMIK), QWERTY, and interlaced QWERTY for shape writing. The goodness of a layout for shape writing has two aspects. For users' initial ease of use the letters should be easy to visually locate. For long term use, however, the layout should maximize the imprecision tolerance and writing flexibility for all words. We present empirical studies for the former and mathematical analyses for the latter. Our results led to a new layout, interlaced QWERTY, which offers excellent separation of word shapes, while still maintaining a low visual search time. Many of the findings in our study also apply to traditional soft keyboards tapped with a stylus or one finger. Copyright 2008 ACM.