T9 (predictive text)
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T9, which stands for Text on 9 keys, is a patented predictive text technology for mobile phones, developed by Tegic Communications, recently acquired by Nuance Communications [1]. It is used on phones from LG, Samsung Electronics, Nokia, Siemens, Sony Ericsson, Sanyo, Sagem and others. It was also used by Texas Instruments PDA Avigo during the late 90s. Its main competitors are iTap, created by Motorola, Zi's eZiText, and SureType, created by RIM.
T9's objective is to make it easier to type text messages. It allows words to be entered by a single keypress for each letter, as opposed to the multi-tap approach used in the older generation of mobile phones in which several letters are associated with each key, and selecting one letter often requires multiple keypresses.
It combines the groups of letters on each phone key with a fast-access dictionary of words. It looks up in the dictionary all words corresponding to the sequence of keypresses and orders them by frequency of use.
As it gains familiarity with the words and phrases the user commonly uses, it speeds up the process by offering the most frequently used words first and then lets the user access other choices with one or more presses of a predefined Next key.
The dictionary can be expanded by adding missing words, enabling them to be recognized in the future. After introducing a new word, the next time the user tries to produce that word T9 will add it to the predictive dictionary.
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[edit] Interface workflow
- Enter a word by tapping one key per letter.
- The word displayed on the screen is not valid until the whole text is typed. Since T9 tries to find matching words while typing, the suggested word may change after each key press.
- If T9 displays a word that is not the one you were looking for, press the Next key to scroll through the possible matches.
- If the wanted word is not in T9’s dictionary, there is an option to add it after visiting all available words with the NEXT key. The word must be typed using the traditional multi-tap method.
[edit] Problems and criticism
Though T9 is available in over 70 languages [1], in Sweden only, there has been recent controversy around the T9 word list. In Swedish, compound words are very common and it has become a fad for people to see what offensive words they might be able to spell out. Ironically, the words are not so offensive that the daily newspapers refuse to report them. For example, one teenage girl was the subject of a number of jokes after T9 confused "dating" with "eating". The sent message read:"He's been much happier since he's been eating me. ;-)"[2]
[edit] Managing the user database (UDB)
The user can manually add words to the UDB (user database) via multi-tap. The implementation of the user database depends on the version of T9 and how T9 is actually integrated on the device. Some phone manufacturers implement a permanent user database, others implement one for the duration of the session. [3]
[edit] Algorithm
In order to achieve compression ratios of close to 1 byte per word, T9 uses an optimized algorithm which maintains the order of words, and partial words (also known as stems) but because of this compression, it over-generates words which are sometimes visible to the user as 'junk words'. This is a side effect of the requirements for small database sizes on the lower end embedded devices.
[edit] Features
Smart punctuation - This feature allows the user to insert sentence and word punctuation using the '1'-key. Depending on the context, smart punctuation inserts sentence punctuation (period) or embedded punctuation (period or hyphen) or word punctuation (apostrophe in can't, won't, isn't as well as the possessive -'s-). Depending on the language T9 also supports word breaking after punctuation to support the -l'-, -n'- etc in French or the -'s- behavior for possessives in English.
User database (UDB) - The UDB is an optional feature which allows words that were explicitly entered by the user to be stored for future reference. The number of words stored depends on the implementation as well as the language.
Reordering - In later versions of T9, the order of the words presented adapts to the usage pattern. For instance in English 4663 matches 'good', 'home', 'gone', 'hood' etc. When the user uses 'home' more often than 'good', eventually the two words will switch position.
Next word prediction - In later versions of T9, information about common word combinations are learned from the user and stored for future predictions.
Word completion - For words entered by the user, word completion can be enabled. When the user enters matching key-presses, in addition to words and stems, the system will also provide completions.
Bi-lingual - In later versions of T9, the user can select a primary and secondary language and matches from both languages are presented. This enables users to write messages in their native as well as a foreign language.
[edit] See also
[edit] Notes
- ^ Nuance - T9 - Datasheets
- ^ ”Rasistiska ord ska tas bort ur mobilernas ordlistor” by Emma Thelénius-Wanler, in Dagens Nyheter, April 16, 2008, http://www.dn.se/DNet/jsp/polopoly.jsp?d=2374&a=761571
- ^ Add your own words (T9.com) http://t9.com/learn/qt-add-your-own-words.asp
