Xerox PARC sued Palm over Graffiti for patent infringement in 1997 [1] [2], having filed a patent for Unistrokes in 1993 [3]. Their patent was ruled invalid due to prior art, Xerox appealed the ruling, and Palm payed Xerox $22.5 million [4]. Research [5] has shown Unistrokes to be somewhat faster than Graffiti.

>Furthermore, the [Unistroke] alphabet's strokes are well distinguished in "sloppiness space", allowing for accurate recognition of not-so-accurate input.

>Unlike Graffiti, Unistrokes gestures bare little resemblance to Roman letters. However, each letter is assigned a short stroke, with frequent letters (e.g., E, A, T, I, R) associated with a straight line. Unistrokes is analogous to touch-typing with a keyboard, as practice will result in high-speed, "eyes-free" input.

>Over twenty fifteen-phrase sessions, text entry speed in the Graffiti group increased from 4.0 wpm to 11.4 wpm. During the same time, text entry speed in the Unistrokes group increased from 4.1 wpm to 15.8 wpm. However, an analysis of variance yielded a lack of statistical difference in entry speed between the two techniques. Participants often performed unnecessary deletions, resulting in high correction rates. In addition, the duration of gesture chart views decreased quickly, but varied widely between participants. Inter-stroke time between the two groups was similar, but the significant difference in stroke duration favoured Unistrokes. The Graffiti alphabet's recognisability endears itself to novice users. However, this study shows that investing the same time learning Unistrokes can result in significantly faster stroke time and higher text entry speed.

Ken Perlin also developed a continuous stylus-based text entry system called Quikwriting [6] [7], which he patented [8]. And there have been various imitations and other questionable patents [9]. It would be interesting to measure how Quikwriting compares with Unistrokes and Graffiti -- it might be faster since it doesn't involve lifting the pen between letters.

[1] http://www.brighthand.com/news/palm-xerox-finally-settle-gra...

[2] http://www.palminfocenter.com/news/8628/xerox-graffiti-lawsu...

[3] https://www.google.com/patents/US5596656

[4] https://en.wikipedia.org/wiki/Graffiti_(Palm_OS)#Lawsuit

[5] http://www.yorku.ca/mack/chi2008b.html

[6] http://mrl.nyu.edu/~perlin/doc/quikwriting/quikwriting.pdf

[7] http://www.mrl.nyu.edu/projects/quikwriting/

[8] https://www.google.com/patents/US6031525

[9] http://shr-devel.shr-project.narkive.com/wIClUJgX/someone-is...