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Gesture Keyboard - User centered design of a unique input device
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for Indic Scripts
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Ashish Krishna , Rahul Ajmera , Sandesh Halarnkar, Prashant Pandit
HP Laboratories India
HPL-2005-56
March 18, 2005*
devnagari text Indic text input presents a unique challenge in the field of keyboard
entry, gesture design because of the number of standalone characters, conjuncts, matras,
keyboard (GKB), and symbols. It poses a huge ch
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Gesture Keyboard - User centered design of a unique input device for Indic Scripts 1 1 Ashish Krishna , Rahul Ajmera Sandesh Halarnkar and Prashant Pandit Human Factors International HP labs th 4 Floor, Chemtex House 24, Salarpuria Arena, Hiranandani Gardens Hosur Main Road, Adugodi, Mumbai – 400 076 Bangalore, India {ashish.krishna, rahul.ajmera}@hp.com {sandesh.halarnkar, prashant.pandit}@hp.com 1 Currently at HP labs Abstract Indic text input presents a unique
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Figure 1: typical computer setup with a gesture keyboard 2.1 Need for a Devnagari input device Computer usage in India is almost entirely in English and is restricted to the English-speaking, upper and upper- middle class people. This stands in direct contrast with the demand for communication in Indian languages. Census data for the year 1991shows that English is the first language for only 0.02% of Indians and second and third language for 8% and 3% respectively. Hindi TV programs c
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Figure 2: Inscript keyboard (with multiple characters on a single key) Commercially the demand for Devnagari input has been patched by the Inscript keyboard. This is essentially a QWERTY keyboard with Devnagari characters mapped onto the keys. The minimum number of characters that are required even representing Devnagari is 54, base consonants (34), vowels (19), and a halant key. This excludes Devnagari numerals and various Vedic symbols and modifiers i.e. Ref, Ru, Half Ra. This issue mani
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3.2 Spatial mapping of gestures In order to limit the technological complexity of recognition and thereby trying to reduce instances of errors, we have mapped the gestures on the coordinates of the writing space. This means that the number of elements that needs to be recognized has been reduced. The same gestures made in different areas of the pad produce different combinations wherein the consonant is selected using the spatial mapping and the modifiers are assigned after recognition o
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3.5 Deleting using the GKB The Devnagari script is very differently from roman scripts because of the conjuncts it forms when Consonant- Consonant-Vowel modifier, Consonant-Vowel-Vowel combination happens. So, in the case of normal ‘backspace’ where 1 unicode is deleted at a time and it becomes very irrational to display the left over characters from conjuncts, which the user never actually wrote. Figure 4: Editing problems eradicated using a horizontal score on the backspace To ov
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4.1 User study 4.1.1 Objective The objective of this exploration was to find the average size users take to write consonants and modifiers (matras) and to find relationship between handwriting styles with different pen grip diameter and tip thickness. 4.1.2 Method Each user was given a Hindi paragraph (76 words) and they had to copy this Hindi corpus in their own handwriting on the provided paper. They were given basic instructions explaining the task and the goal of the experim
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Figure 6: Pens used for study (middle one is the stylus) 4.1.4.3 Hindi corpus used: The Hindi paragraph used for this user study was taken from the BBC’s Hindi news portal (http://www.bbc.co.uk/hindi/news/020419_vajpayee_ac.shtml) and was modified a bit so that we could get all the nuances of Hindi matras in the corpus. Figure 7: Hindi Corpus 4.1.5 Evaluation method Subjects’ hands written samples were collected and analyzed by measuring the base consonants and the modifiers
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th Bottom strip. Since, the dataset was very distributed, we adhered to the 90 percentile data so that almost all of the population could be accommodated. sizes in mms Top Strip Size Plot 90th percentile data 4.5 4.19 4 3.5 3 2.5 2 top strip 1.5 1 0.5 0 0 5 10 15 20 25 Participants sizes in mms Core Strip Size Plot 90th percentile data 6 4.63 5 4 3 2 1 0 0 5 10 15 20 25 Participants size in mms size in mms
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sizes in mms Bottom Strip Size Plot 90th percentile data 4 3 3 2 1 0 0 5 10 15 20 25 Participants Figure 9: Graphs showing cluster data for handwriting samples (X axis shows the size in mm and Y axis denotes the no of participants) 4.1.7 Results The final gesturable keypad sizes, which is analogous to handwriting was 11.82 mm. The core strip was 4.63 mm, space required for top strip was 4.13 mm, and the space required for the bottom strip was 3 mm. We didn’t take the left and right
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5 Conclusions This keyboard has been accepted quite well with the novice users who have never used Devnagari keyboard before. In our small sessions of user studies they all seem to be satisfied and were able to achieve a speed of 10-12 syllables per minute. Also after a dedicated usage of an hour everyday for 2-3 days they were able to go up to 25-30 syllables per minute. The keyboard has a high satisfaction factor associated with it because writing with pen on paper (in our case the k
