Keyboard system with automatic correction

Abstract

A text entry system uses word-level analysis to automatically correct inaccuracies in user keystroke entries. The system determines one or more alternative textual interpretations of each sequence of inputs detected within an auto-correcting keyboard region. The actual contract locations for the keystrokes may occur outside the boundaries of the specific keyboard key regions associated with the actual characters of the word interpretations proposed for selection, where the distance from each contact location to each corresponding intended character may increase with the expected frequency of the intended word in the language or in a particular context. Each such sequence corresponds to a complete word, and the user can easily select the intended word from among the generated interpretations. Once the user selects the desired string, it is automatically accepted for output and the next input detected starts a new input sequence corresponding to the entry of a next word.

Claims

What is claimed is:

1. A text entry system comprising:

(a) a user Input device comprising a touch sensitive surface including an auto-correcting keyboard region comprising a plurality of the characters of an alphabet, wherein each of the plurality of characters corresponds to a location with known coordinates in the auto-correcting keyboard region, wherein each time a user contacts the user input device within the auto-correcting keyboard region, a location associated with the user contact is determined and the determined contact location is added to a current input sequence of contact locations;

(b) a memory containing a plurality of objects, wherein each object is further associated with a frequency of use, and wherein each of the plurality of objects in memory is further associated with one or a plurality of predefined groupings of objects;

(c) an output device with a text display area; and

(d) a processor coupled to the user input device, memory, and output device, said processor comprising:

(i) a distance value calculation component which, for each determined contact location in the input sequence of contacts, calculates a set of distance values between the contact locations and the known coordinate locations corresponding to one or a plurality of characters within the auto-correcting keyboard region;

(ii) a word evaluation component which, for each generated input sequence, identifies one or a plurality of candidate objects in memory, and for each of the one or a plurality of identified candidate objects, evaluates each identified candidate object by calculating a matching metric based on the calculated distance values and the frequency of use associated with the object, and ranks the evaluated candidate objects based on the calculated matching metric values;

(III) a selection component for identifying one or a plurality of candidate objects according to their evaluated ranking, presenting the identified objects to the user, and enabling the user to select one of the presented objects for output to the text display area on the output device; and

(iv) a frequency promotion component for increasing a relative frequency of use value associated with each object in memory as a function of the number of times the object is selected by the user for output to the text display area on the output device and for decreasing a relative frequency of use value associated with each object in memory as a function of the number of times the object is passed over by the user.

2. The text entry system of claim 1, wherein the word evaluation component, for each generated input sequence, limits the number of objects for which a matching metric is calculated by identifying one or a plurality of candidate groupings of the objects in memory, and for one or a plurality of objects associated with each one or a plurality of identified candidate groupings of objects, calculates a matching metric based on the calculated distance values and the frequency of use associated with each candidate object, and ranks the evaluated candidate objects based on the calculated matching metric values.

3. The system of claim 1, wherein the characters of the alphabet are arranged on the auto-correcting keyboard region in approximately a standard "QWERTY" layout.

4. The system of claim 3, wherein the width to height ratio of the auto-correcting keyboard region is approximately 2 to 1.

5. The system of claim 3, wherein the width to height ratio of the auto-correcting keyboard region is less than 2 to 1.

6. The system of claim 3, wherein one or a plurality of the characters arranged on the auto-correcting keyboard region are illegible.

7. The system of claim 1, wherein said auto-correcting keyboard region includes one or a plurality of known locations associated with one or a plurality of punctuation characters, wherein said memory includes one or a plurality of objects in memory which include one or a plurality of the punctuation characters associated with locations in said auto-correcting keyboard region.

8. The system of claim 1, wherein objects in memory are further associated with one or a plurality of modules, wherein each module comprises a set of objects with one or a plurality of common characteristics.

9. The system of claim 8, wherein the text entry system comprises a module selector whereby a user can determine which modules are to be evaluated by the word evaluation component in order to identify candidate objects.

10. The system of claim 8, wherein the plurality of modules comprises word stem modules and suffix modules, wherein each word stem module comprises a logical organization of uninflected word stem objects, and wherein each suffix module comprises a logical organization of suffixes which can be appended to word stems to form inflected words, whereby each word stem module is associated with one or a plurality of suffix modules, whereby whenever the word evaluation component calculates a matching metric value for a given word stem in a given word stem module with respect to an initial sequence of contacts within an input sequence such that the calculated matching metric value ranks higher than a predetermined threshold, the word evaluation component evaluates the remaining contacts of the input sequence with respect to the associated suffix modules, whereby whenever the word evaluation component calculates a matching metric value for a given suffix in one of said associated suffix modules that ranks higher than a second predetermined threshold, said suffix is appended to said word stem to form a completed word corresponding to a matching metric value that is a function of said determined word stem matching metric value and said determined suffix matching metric value.

11. The system of claim 1, wherein the word evaluation component calculates the matching metric for each candidate object by summing the distance values calculated from each contact location in the input sequence to the location assigned to the character in the corresponding position of the candidate object, and applying a weighting function according to the frequency of use associated with the object.

12. The system of claim 11, wherein each character of the alphabet associated with the auto-correcting keyboard region is assigned a Cartesian coordinate and wherein the distance value calculation component calculates the distance between the contact location and the location corresponding to a character according to standard Cartesian coordinate distance analysis.

13. The system of claim 11, wherein each character of the alphabet associated with the auto-correcting keyboard region is assigned a Cartesian coordinate and wherein the distance value calculation component calculates the distance between the contact location and the location corresponding to a character as the square of the standard Cartesian coordinate distance.

14. The system of claim 11, wherein the distance values are placed in a table.

15. The system of claim 11, wherein each location on the auto-correcting keyboard region is defined by a horizontal and a vertical coordinate, and wherein the distance value between a contact location and the known coordinate location corresponding to a character comprises a horizontal and a vertical component, wherein the vertical component is adjusted by a weighting factor in calculating the distance of the contact location from the character.

16. The system of claim 11, wherein the frequency of use associated with each candidate object in memory comprises the ordinal ranking of the object with respect to other objects in memory, wherein an object associated with a higher relative frequency corresponds to a numerically lower ordinal ranking.

17. The system of claim 16, wherein the frequency weighting function applied by the word evaluation component to the summed distance values for a candidate object comprises multiplying the sum of the distance values by the base 2 logarithm of the ordinal ranking of the object.

18. The system of claim 11, wherein the word evaluation component adds an increment value to the sum of the distance values prior to applying a weighting function according to the frequency of use associated with the candidate object.

19. The system of claim 18, wherein the increment value is a fixed value that is approximately twice the average distance between adjacent locations on the auto-correcting keyboard region corresponding to characters.

20. The system of claim 2, wherein objects in memory are stored such that objects are classified into groupings comprising objects of the same length.

21. The system of claim 20, wherein the word evaluation component limits the number of objects for which a matching metric is calculated by initially identifying candidate groupings of objects of the same length as the number of inputs in the input sequence.

22. The system of claim 21, wherein if fewer than a threshold number of candidate objects are evaluated to have a matching metric score better than a threshold value, the word evaluation component identifies candidate groupings of objects of progressively longer lengths and calculates the matching metric for the objects in the identified groupings until said threshold number of candidate objects are evaluated to have a matching metric score better than said threshold.

23. The system of claim 22, wherein the word evaluation component calculates the matching metric for each candidate object by summing the distance values calculated from each contact location in the input sequence to the location assigned to the character in the corresponding position of the candidate object and adding an increment value, and applying to this sum a weighting function according to the frequency of use associated with the object, and wherein the increment value added to the sum of the distance values is a value that is based on the difference between the number of characters in the candidate object and the number of inputs in the current input sequence.

24. The system of claim 2, wherein the word evaluation component calculates the matching metric for each candidate object by summing the distance values calculated from each contact location in the input sequence to the location assigned to the character in the corresponding position of the candidate object, and applying a weighting function according to the frequency of use associated with the object.

25. The system of claim 24, wherein the frequency of use associated with each candidate object in memory comprises the ordinal ranking of the object with respect to other objects in one or a plurality of sub-groupings in memory with which said object is associated, wherein an object associated with a higher relative frequency corresponds to a numerically lower ordinal ranking.

26. The system of claim 24, wherein for each calculated distance value between a contact location in the input sequence and the known coordinate location corresponding to a character within the auto-correcting keyboard region wherein said calculated distance exceeds a threshold distance value, for each object in memory in which said character occurs at a position in the sequence of the characters of said object corresponding to the position of said contact location in said input sequence, said object is ranked by the word evaluation component as an object that is excluded from presentation to the user for selection.

27. The system of claim 26, wherein one or a plurality of the identified candidate groupings of the objects in memory comprise objects that are excluded from presentation to the user for selection, wherein at least one of the calculated distance values included in the calculated sum of distance values for each object in said one or identified candidate groupings of objects exceeds a threshold distance value.

28. The system of claim 27, wherein the auto-correcting keyboard region is separated into two or more predefined clustering regions, each of which contains the known locations of one or a plurality of characters, and wherein each objects in memory is assigned to a predefined group according to which of said two or more predefined clustering regions contain the known locations corresponding to one or a plurality of the initial characters of said object.

29. The system of claim 28, wherein the auto-correcting keyboard region is separated into three predefined clustering regions, and wherein each object in memory is assigned to one of nine predefined groupings based which of the three predefined clustering regions contain the known locations corresponding to each of the first two characters of said object.

30. The system of claim 1, wherein for each character corresponding to a known location in the auto-correcting keyboard region, a region is predefined around one or a plurality of said known locations-wherein the distance between an input contact location falling within said predefined region and the known character location within said predefined region is calculated as a distance of zero.

31. The system of claim 30, wherein the relative sizes of said predefined regions correspond to the relative frequencies of occurrence of the characters associated with the known locations within said predefined regions.

32. The system of claim 30, wherein said predefined region around the known location of a character corresponds to a displayed key on the touch screen.

33. The system of claim 1, wherein at least one of the locations with known coordinates in the auto-correcting keyboard region corresponds to a plurality of characters, one or a plurality of which include various diacritic marks, wherein the plurality of characters comprise variant forms of a single base character, and wherein objects in memory are stored with their correct accented characters.

34. The system of claim 1, wherein the selection component presents the identified one or a plurality of candidate objects for selection by the user in a candidate object list in the text display area.

35. The system of claim 34, wherein the selection component identifies the highest ranked candidate object and presents the identified object in the candidate object list in the position nearest to the auto-correcting keyboard region.

36. The system of claim 1, wherein a user selection of a character that is associated with a contact outside of the auto-correcting keyboard region accepts and outputs the determined highest ranked candidate object at a text insertion point in the text display area prior to outputting the selected character at the text insertion point in the text display area.

37. The system of claim 1, wherein user selection of an object for output at a text insertion point in the text display area terminates the current input sequence such that the next contact within the auto-correcting keyboard region starts a new input sequence.

38. The system of claim 1, wherein the selection component detects a distinctive manner of selection that is used to select a candidate object, and wherein upon detecting that an object has been selected through said distinctive manner, the system replaces the current input sequence of actual contact locations with an input sequence of contact locations corresponding to the coordinate locations of the characters comprising the selected object, and wherein a next contact in the auto-correcting keyboard region is appended to the current input sequence.

39. The system of claim 1, wherein the word evaluation component determines, for each determined contact location in each input sequence of contact locations, the closest known location corresponding to a character, and constructs an exact typing object composed of said determined corresponding characters in the order corresponding to the input sequence of contact locations.

40. The system of claim 39, wherein for each input sequence of contact locations, the selection component presents said exact typing object to the user for selection.

41. The system of claim 40, wherein when the user selects said exact typing object for output to the text display area on the output device and said exact typing object is not already included as one of the objects in memory, said exact typing object is added to the memory.

42. The system of claim 40, wherein prior to displaying said exact typing object to the user for selection, the selection component compares the exact typing object to a database of offensive objects, each of which is associated with an acceptable alternative object for display, and if a match is found, replaces the exact typing object with the associated acceptable object for presentation to the user.

43. The system of claim 1, wherein the selection component identifies the highest ranked candidate object and presents the identified object at the text insertion point in the text display area on the output device.

44. The system of claim 43, wherein the text entry system includes a select key region associated with an object selection function, wherein when said select key region is contacted, the object presented at the text insertion point in the text display area on the output device is replaced with next highest ranked object of the identified one or a plurality of candidate objects.

45. The system of claim 1, wherein the text entry system includes a delete key region associated with a delete function, wherein when the current input sequence includes at least one contact and said delete key region is contacted, the last input contact from the current input sequence of contacts is deleted, without terminating the current input sequence.

46. The system of claim 1, wherein the text entry system includes an Edit Word key region associated with an Edit Word function, wherein when no current input sequence exists and said Edit Word key region is contacted,

when the text insertion point in the text display area on the output device is contained within a previously output word, the system establishes a new current input sequence consisting of a sequence of contact locations corresponding to the coordinate locations associated with the characters of said word, and

when the text insertion point in the text display area on the output device is located between two previously output words, the system establishes a new current input sequence consisting of a sequence of contact locations corresponding to the coordinate locations associated with the characters of the word adjacent to the text insertion point, and

wherein the text entry system processes said new current input sequence and determines a corresponding ranking of new candidate objects, and

wherein selection of one of the new candidate objects replaces the previously output word used to establish said new current input sequence.

47. The system of claim 1, wherein as the user enters an input sequence by performing a sequence of contact actions within the auto-correcting keyboard region, the processor determines the location associated with each user contact action by recording each contact action in the sequence as an indexed primary set of a fixed number of two or more regularly spaced contact points along the path traced out by the user contact action, and by assembling two or more corresponding secondary sets of contact points by taking, for each of the two or more possible primary index values, the sequence of contact points having the same index value, one from each recorded indexed primary set of contact points, and by determining with respect to each word that is selected by the user for output, a minimizing primary index value that identifies the assembled secondary set of contact points for which the calculated distance between the assembled secondary set of contact points and the known locations corresponding to the characters of the selected word is minimized, and whereby for a next input sequence of user contact actions, the distance value calculation component calculates distance values based on a sequence of contact locations determined as the secondary set of contact point locations assembled from said next input sequence of contact actions corresponding to the determined minimizing primary index value.

48. The system of claim 47, wherein for a plurality of user input sequences, the distance value calculation component computes a running average of the distance calculations for each of the two or more assembled secondary sets corresponding to the two or more primary index values, and whereby for a next input sequence of contact actions, the distance value calculation component calculates distance values based on a sequence of contact locations determined as the secondary set of contact point locations assembled from said next input sequence of contact actions corresponding to the minimizing primary index value determined with respect to said computed running averages.

49. The system of claim 48, wherein for each primary index value, the distance value calculation component computes a running average of the horizontal and vertical components of the offset of the coordinate location corresponding to each character of each selected word with respect to the coordinate location of each corresponding recorded indexed contact point, and wherein in performing distance calculations for the word evaluation component, the distance value calculation component adjusts the horizontal and vertical coordinates of each recorded indexed contact point by an amount that is a function of the average horizontal and vertical offsets computed with respect to the corresponding primary index value.

50. The system of claim 1, wherein for each input contact location, the distance value calculation component computes a running average of the horizontal and vertical components of the offset of the coordinate location corresponding to each character of each selected word with respect to the coordinates of each corresponding input contact location, and wherein in performing distance calculations for the word evaluation component, the distance value calculation component adjusts the horizontal and vertical coordinates of each input contact location by amounts that are functions of the computed average signed horizontal and vertical offsets.

51. The system of claim 2, wherein the processor further comprises a frequency promotion component for adjusting the frequency of use associated with each object in memory as a function of the number of times the object is selected by the user for output to the text display area on the output device.

52. The system of claim 1, wherein when a threshold number of contact locations in the input sequence are further than a threshold maximum distance from the corresponding character in the sequence of characters comprising a given candidate object, said object is identified as no longer being a candidate object for the selection component.

53. The system of claim 1, wherein the frequency of use associated with each object in memory comprises the ordinal ranking of the object with respect to other objects in memory, wherein an object associated with a higher relative frequency corresponds to a numerically lower ordinal ranking, and wherein when an object is selected for output by the user, the frequency promotion component adjusts the ordinal ranking associated with said selected object by an amount that is a function of the ordinal ranking of said object prior to said adjustment.

54. The system of claim 53, wherein the function used by the frequency promotion component to determine the amount by which the ordinal ranking associated with a selected object is adjusted reduces said amount for objects with ordinal rankings that are associated with relatively higher frequencies of use.

55. The system of claim 1, wherein the frequency promotion component analyzes additional information files that are accessible to the text entry system to identify new objects contained in said files that are not included among the objects already in said memory of said text entry system, and wherein said newly identified objects are added to the objects in memory as objects that are associated with a low frequency of use.

56. The system of claim 55, wherein the frequency of use associated with a newly identified object that is added to the objects in memory is adjusted by the frequency promotion component as a function of the number of times that the newly identified object is detected during the analysis of said additional information files.

57. The system of claim 1, wherein when an object is selected by the user for output to the text display area on the output device, the frequency promotion component increases the value of the frequency associated with the selected object by a relatively large increment, and decreases by a relatively small decrement the frequency associated with unselected objects that are associated with the same grouping as the selected object.

58. The system of claim 1, wherein information regarding the capitalization of one or a plurality of objects is stored along with the objects in memory and wherein the selection component presents each identified object in a preferred form of capitalization according to the stored capitalization information.

59. The system of claim 1, wherein one or a plurality of objects in memory are associated with a secondary object in memory comprising a sequence of one or a plurality of letters or symbols, and wherein when the selection component identifies one of said objects for presentation to the user based on the matching metric calculated by the word evaluation component, the selection component presents the associated secondary object for selection.

60. A text entry system comprising:

(a) a user input device comprising a touch sensitive surface including an auto-correcting keyboard region comprising a plurality of the characters of an alphabet, wherein each of the plurality of characters corresponds to a location with known coordinates in the auto-correcting keyboard region, wherein each time a user contacts the user input device within the auto-correcting keyboard region, a location associated with the user contact is determined and the determined contact location is added to a current input sequence of contact locations;

(b) a memory containing a plurality of objects, wherein each object is further associated with a frequency of use, and wherein each of the plurality of objects In memory Is further associated with one or a plurality of predefined groupings of objects;

(c) an output device with a text display area; and

(d) a processor coupled to the user input device, memory, and output device, said processor comprising:

(i) a distance value calculation component which, for each generated key activation event location in the input sequence of key activation events, calculates a set of distance values between the key activation event location and the known coordinate locations corresponding to one or a plurality of keys within the auto-correcting keyboard region;

(ii) a word evaluation component which, for each generated input sequence, identifies one or a plurality of candidate objects in memory, and for each of the one or a plurality of identified candidate objects, evaluates each identified candidate object by calculating a matching metric based on the calculated distance values and the frequency of use associated with the object, and ranks the evaluated candidate objects based on the calculated matching metric values;

(iii) a selection component for identifying one or a plurality of candidate objects according to their evaluated ranking, presenting the identified objects to the user, and enabling the user to select one of the presented objects for output to the text display area on the output device; and

(iv) a frequency promotion component for increasing a relative frequency of use value associated with each object in memory as a function of the number of times the object is selected by the user for output to the text display area on the output device and for decreasing a relative frequency of use value associated with each object in memory as a function of the number of times the object is passed over by the user.

61. The text entry system of claim 60, wherein the word evaluation component, for each generated input sequence, limits the number of objects for which a matching metric is calculated by identifying one or a plurality of candidate groupings of the objects in memory, and for one or a plurality of objects associated with each one or a plurality of identified candidate groupings of objects, calculates a matching metric based ion the calculated distance values and the frequency of use associated with each candidate object, and ranks the evaluated candidate objects on the calculated matching metric values.

62. The system of claim 60, wherein the keys associated with the characters of the alphabet are arranged in the auto-correcting keyboard region in approximately a standard "QWERTY" layout.

63. The system of claim 60, wherein when a key activation event is detected comprising the simultaneous activation of a plurality of adjacent keys in the auto-correcting keyboard region, a location corresponding to said key activation event is determined as a function of the locations of the simultaneously activated keys, and said determined location is appended to the current input sequence of the locate of the key activation events.

64. The system of claim 63, wherein the function used to determine the location of said key activation event comprises the computation of the location corresponding to the center of the locations of the simultaneously activated keys.

65. The system of claim 64, wherein the function used to determine the location of said key activation event comprises the computation of the location corresponding to the weighted center of gravity of the locations of the simultaneously activated keys, wherein the weights associated with each of the keys in the auto-correcting keyboard region correspond to the relative frequencies of occurrence of the characters associated with the keys, wherein said relative frequencies are determined with respect to the frequencies of occurrence of the characters in the objects in memory.

66. The system of claim 60, wherein when a key activation event is detected comprising the activation of a plurality of adjacent keys in the auto-correcting keyboard region within a predetermined threshold period of time, wherein at all times during said key activation event at least one of said plurality of adjacent keys is activated and wherein at any moment during said key activation event that any subset of said plurality of keys is simultaneously activated, said simultaneously activated subset of keys comprises keys that are contiguously adjacent, a location corresponding to said key activation event is determined as a function of the locations of the entire plurality of adjacent keys detected during said key activation event, and said determined location is appended to the current input sequence of the locations of the key activation events.

67. The system of claim 66, wherein the function used to determine the location of said key activation event comprises the computation of the location corresponding to the center of the locations of the simultaneously activated keys.

68. The system of claim 67, wherein the function used to determine the location of said key activation event comprises the computation of the location corresponding to the weighted center of gravity of the locations of the simultaneously activated keys, wherein the weights associated with each of the keys in the auto-correcting keyboard region correspond to the relative frequencies of occurrence of the characters associated with the keys, wherein said relative frequencies are determined with respect to the frequencies of occurrence of the characters in the objects in memory.

69. The system of claim 60, wherein said auto-correcting keyboard region includes one or a plurality of keys associated with one or a plurality of punctuation characters, wherein said memory includes one or a plurality of objects in memory which include one or a plurality of the punctuation characters associated with keys in said auto-correcting keyboard region.

70. The system of claim 60, wherein the word evaluation component calculates the matching metric for each candidate object by summing the distance values calculated from determined location in the input sequence to the known location of the key corresponding to the character in the corresponding position of the candidate object, and applying a weighting function according to the frequency of use associated with the object.

71. The system of claim 60, wherein at least one of the keys in the auto-correcting keyboard region corresponds to a plurality of characters, one or a plurality of which include various diacritic marks, wherein the plurality of characters comprise variant forms of a single base character, and wherein objects in memory are stored with their correct accented characters.

72. The system of claim 60, wherein the selection component presents the identified one or a plurality of candidate objects for selection by the user in a candidate object list in the text display area.

73. The system of claim 72, wherein the selection component identifies the highest ranked candidate object and presents the identified object in the candidate object list in the position nearest to the auto-correcting keyboard region.

74. The system of claim 72, wherein activation of a key that is associated with a character, wherein said key is not included within the auto-correcting keyboard region, accepts and outputs the determined highest ranked candidate object at a text insertion point in the text display area prior to outputting the selected character at the text insertion point in the text display area.

75. The system of claim 72, wherein user selection of an object for output at a text insertion point in the text display area terminates the current input sequence such that the next key activation event within the auto-correcting keyboard region starts a new input sequence. objects in memory, and for one or a plurality of objects associated with each one or a plurality of identified candidate groupings of objects, calculates a matching metric based on the calculated distance values and the frequency of use associated with each candidate object, and ranks the evaluated candidate objects based on the calculated matching metric values.

Description

TECHNICAL FIELD OF THE INVENTION

The invention provides keyboard systems that auto-correct "sloppy" text entry due to errors in touching a keyboard or screen. More specifically, the invention provides a reduced keyboard such as those implemented on a touch-sensitive panel or display screen and to mechanical keyboard systems, using word-level analysis to resolve inaccuracies (sloppy text entry) in user entries. This invention is in the field of keypad input preferably for small electronic devices.

BACKGROUND OF THE INVENTION

For many years, portable computers have been getting smaller and smaller. The principal size-limiting component in the effort to produce a smaller portable computer has been the keyboard. If standard typewriter-size keys are used, the portable computer must be at least as large as the keyboard. Miniature keyboards have been used on portable computers, but the miniature keyboard keys have been found to be too small to be easily or quickly manipulated with sufficient accuracy by a user.

Incorporating a full-size keyboard in a portable computer also hinders true portable use of the computer. Most portable computers cannot be operated without placing the computer on a flat work surface to allow the user to type with both hands. A user cannot easily use a portable computer while standing or moving. In the latest generation of small portable computers, called Personal Digital Assistants (PDAs), companies have attempted to address this problem by incorporating handwriting recognition software in the PDA. A user may directly enter text by writing on a touch-sensitive panel or display screen. This handwritten text is then converted into digital data by the recognition software. Unfortunately, in addition to the fact that printing or writing with a pen is in general slower than typing, the accuracy and speed of the handwriting recognition software has to date been less than satisfactory. To make matters worse, today's handheld computing devices which require text input are becoming smaller still. Recent advances in two-way paging, cellular telephones, and other portable wireless technologies has led to a demand for small and portable two-way messaging systems, and especially for systems which can both send and receive electronic mail ("e-mail").

It would therefore be advantageous to develop a much smaller keyboard for entry of text into a computer. As the size of the keyboard is reduced, the user encounters greater difficulty selecting the character of interest. In general there are two different types of keyboards utilized in such portable devices. One is the familiar mechanical keyboard consisting of a set of mechanical keys that are activated by depressing them with a finger or thumb. However, these mechanical keyboards tend to be significantly smaller than the standard sized keyboards associated with typewriters, desktop computers, and even "laptop" computers. As a result of the smaller physical size of the keyboard, each key is smaller and in closer proximity to neighboring keys. This increases the likelihood that the user will depress an unintended key, and the likelihood of keystroke errors tends to increase the faster the user attempts to type.

Another commonly used type of keyboard consists of a touch-sensitive panel on which some type of keyboard overlay has been printed, or a touch-sensitive display screen on which a keyboard overlay can be displayed. Depending on the size and nature of the specific keyboard, either a finger or a stylus can be used to contact the panel or display screen within the area associated with the key that the user intends to activate. Due to the reduced size of many portable devices, a stylus is often used in order to attain sufficient accuracy in contacting the keyboard to activate each intended key. Here again, the small overall size of such keyboards results in a small area being associated with each key so that it becomes quite difficult for the average user to type quickly with sufficient accuracy.

One area of prior development in mechanical keyboards has considered the use of keys that are much smaller than those found on common keyboards. With smaller keys, the user must take great care in controlling each key press. One approach (U.S. Pat. No. 5,612,690) proposes a system that uses up to four miniature keys in unison to define primary characters (the alphabet) and nests secondary character rows (like numbers) between primary character rows. Selecting a secondary character involves depressing the miniature key from each of the surrounding primary characters. Grouping the smaller keys in this fashion creates a larger apparent virtual key composed of four adjacent smaller keys, such that the virtual key is large enough to be depressed using a finger. However, the finger must contact the keys more or less precisely on the "cross-hairs" of the boundaries between the four adjacent keys in order to depress them in unison. This makes it still difficult to type quickly with sufficient accuracy.

Another area of prior development in both touch screen and mechanical keyboards has considered the use of a much smaller quantity of full-size keys. With fewer keys, each single key press must be associated with a plurality of letters, such that each key activation is ambiguous as to which letter is intended. As suggested by the keypad layout of a touch-tone telephone, many of the reduced keyboards have used a 3-by-4 array of keys, where each key is associated with three or four characters (U.S. Pat. No. 5,818,437). Several approaches have been suggested for resolving the ambiguity of a keystroke sequence on such a keyboard. While this approach has merit for such keyboards with a limited number of keys, it is not applicable to reduced size keyboards with a full complement of keys.

Another approach in touch screen keyboards has considered analyzing the immediately preceding few characters in order to determine which character should be generated for a keystroke that is not close to the center of the display location of a particular character (U.S. Pat. No. 5,748,512). When the keyboard is displayed on a small touch screen, keystrokes that are off-center from a character are detected. Software compares the possible text strings of probable sequences of two or three typed characters against known combinations, such as a history of previously typed text or a lexicon of text strings rated for their frequency within a context. When the character generated by the system is not the character intended by the user, the user must correct the character before going on to select the a following character, because the generated character will be used to determine probabilities for the following keystroke.

The fundamental problem is that the specific activations that result from a user's attempts to activate the keys of a keyboard do not always precisely conform to the intentions of the user. On a touch screen keyboard, the user's finger or stylus may hit the wrong character or hit between keys in a boundary area not associated with a specific character. With a miniaturized mechanical keyboard, a given keypress may activate the wrong key, or may activate two or more keys either simultaneously or with a "roll-over" motion that activates adjacent keys in a rapid sequence. Other examples include common keyboards operated by users with limited ranges of motion or motor control, where there is a limited ability to consistently strike any particular space or key, or where the limb (such as in the case of an amputee, or the use of gloved hands or gloved fingers) or the device used to make the entry (such as a stylus) is far larger than the targeted key or character space.

SUMMARY OF THE INVENTION

The present invention provides an enhanced text entry system that uses word-level disambiguation to automatically correct inaccuracies in user keystroke entries. Specifically, the present invention provides a text entry system comprising:

(a) a user input device comprising a touch sensitive surface including an auto-correcting keyboard region comprising a plurality of the characters of an alphabet, wherein each of the plurality of characters corresponds to a location with known coordinates in the auto-correcting keyboard region, wherein each time a user contacts the user input device within the auto-correcting keyboard region, a location associated with the user contact is determined and the determined contact location is added to a current input sequence of contact locations;

(b) a memory containing a plurality of objects, wherein each object is a string of one or a plurality of characters forming a word or a part of a word, wherein each object is further associated with a frequency of use;

(c) an output device with a text display area; and

(d) a processor coupled to the user input device, memory, and output device, said processor comprising:

(i) a distance value calculation component which, for each determined contact location in the input sequence of contacts, calculates a set of distance values between the contact locations and the known coordinate locations corresponding to one or a plurality of characters within the auto-correcting keyboard region;

(ii) a word evaluation component which, for each generated input sequence, identifies one or a plurality of candidate objects in memory, and for each of the one or a plurality of identified candidate objects, evaluates each identified candidate object by calculating a matching metric based on the calculated distance values and the frequency of use associated with the object, and ranks the evaluated candidate objects based on the calculated matching metric values; and

(iii) a selection component for (a) identifying one or a plurality of candidate objects according to their evaluated ranking, (b) presenting the identified objects to the user, enabling the user to select one of the presented objects for output to the text display area on the output device.

Preferably, the selection component further comprises (c) resetting the current input sequence of contact locations to an empty sequence upon detecting the selection by the user of one of the presented objects for output to the text display area on the output device.

Preferably, (a) each of the plurality of objects in memory is further associated with one or a plurality of predefined groupings of objects; and (b) the word evaluation component, for each generated input sequence, limits the number of objects for which a matching metric is calculated by identifying one or a plurality of candidate groupings of the objects in memory, and for one or a plurality of objects associated with each of the one or a plurality of identified candidate groupings of objects, calculates a matching metric based on the calculated distance values and the frequency of use associated with each candidate object, and ranks the evaluated candidate objects based on the calculated matching metric values. This reduces the calculation required since, conversely, one or more groupings of objects are identified as containing no candidate objects for a given input sequence of contacts, such that a matching metric need not be calculated for any object in the groupings so identified.

Preferably, the characters of the alphabet are arranged on the auto-correcting keyboard region in approximately a standard "QWERTY" layout. Most preferably, the width to height ratio of the auto-correcting keyboard region is approximately 2 to 1, or the width to height ratio of the auto-correcting keyboard region is less than 2 to 1. In one embodiment, one or a plurality of the characters arranged on the auto-correcting keyboard region are illegible.

Preferably, the auto-correcting keyboard region includes one or a plurality of known locations associated with one or a plurality of punctuation characters, wherein the memory includes one or a plurality of objects in memory which include one or a plurality of the punctuation characters associated with locations in the auto-correcting keyboard region. Preferably, the objects in memory are further associated with one or a plurality of modules, wherein each module comprises a set of objects with one or a plurality of common characteristics. In one embodiment, the text entry system comprises a module selector whereby a user can determine which modules are to be evaluated by the word evaluation component in order to identify candidate objects. In another embodiment, the plurality of modules comprises word stem modules and suffix modules, wherein each word stem module comprises a logical organization of uninflected word stem objects, and wherein each suffix module comprises a logical organization of suffixes which can be appended to word stems to form inflected words, whereby each word stem module is associated with one or a plurality of suffix modules, whereby whenever the word evaluation component calculates a matching metric value for a given word stem in a given word stem module with respect to an initial sequence of contacts within an input sequence such that the calculated matching metric value ranks higher than a predetermined threshold, the word evaluation component evaluates the remaining contacts of the input sequence with respect to the associated suffix modules, whereby whenever the word evaluation component calculates a matching metric value for a given suffix in one of said associated suffix modules that ranks higher than a second predetermined threshold, said suffix is appended to said word stem to form a completed word corresponding to a matching metric value that is a function of said determined word stem matching metric value and said determined suffix matching metric value.

Preferably, the word evaluation component calculates the matching metric for each candidate object by summing the distance values calculated from each contact location in the input sequence to the location assigned to the character in the corresponding position of the candidate object, and applying a weighting function according to the frequency of use associated with the object. In addition, each character of the alphabet associated with the auto-correcting keyboard region is assigned a Cartesian coordinate and wherein the distance value calculation component calculates the distance between the contact location and the location corresponding to a character according to standard Cartesian coordinate distance analysis. Further, each character of the alphabet associated with the auto-correcting keyboard region is assigned a Cartesian coordinate and wherein the distance value calculation component calculates the distance between the contact location and the location corresponding to a character as the square of the standard Cartesian coordinate distance. The distance values are placed in a table. In addition, each location on the auto-correcting keyboard region is defined by a horizontal and a vertical coordinate, and wherein the distance value between a contact location and the known coordinate location corresponding to a character comprises a horizontal and a vertical component, wherein the vertical component is adjusted by a weighting factor in calculating the distance of the contact location from the character. The word evaluation component adds an increment value to the sum of the distance values prior to applying a weighting function according to the frequency of use associated with the candidate object. Most preferably, the increment value is a fixed value that is approximately twice the average distance between adjacent locations on the auto-correcting keyboard region corresponding to characters. The frequency of use associated with each candidate object in memory comprises the ordinal ranking of the object with respect to other objects in memory, wherein an object associated with a higher relative frequency corresponds to a numerically lower ordinal ranking. Most preferably, the frequency weighting function applied by the word evaluation component to the summed distance values for a candidate object comprises multiplying the sum of the distance values by the base 2 logarithm of the ordinal ranking of the object.

Preferably, objects in memory are stored such that the objects are classified into groupings comprising objects of the same length. The word evaluation component limits the number of objects for which a matching metric is calculated by initially identifying candidate groupings of objects of the same length as the number of inputs in the input sequence. Most preferably, if fewer than a threshold number of candidate objects are evaluated to have a matching metric score better than a threshold value, the word evaluation component identifies candidate groupings of objects of progressively longer lengths and calculates the matching metric for the objects in the identified groupings until said threshold number of candidate objects are evaluated to have a matching metric score better than said threshold. Further, the word evaluation component calculates the matching metric for each candidate object by summing the distance values calculated from each contact location in the input sequence to the location assigned to the character in the corresponding position of the candidate object and adding an increment value, and applying to this sum a weighting function according to the frequency of use associated with the object, and wherein the increment value added to the sum of the distance values is a value that is based on the difference between the number of characters in the candidate object and the number of inputs in the current input sequence.

Preferably, the word evaluation component calculates the matching metric for each candidate object by summing the distance values calculated from each contact location in the input sequence to the location assigned to the character in the corresponding position of the candidate object, and applying a weighting function according to the frequency of use associated with the object. Most preferably, the frequency of use associated with each candidate object in memory comprises the ordinal ranking of the object with respect to other objects in one or a plurality of sub-groupings in memory with which said object is associated, wherein an object associated with a higher relative frequency corresponds to a numerically lower ordinal ranking. In addition, for each calculated distance value between a contact location in the input sequence and the known coordinate location corresponding to a character within the auto-correcting keyboard region wherein said calculated distance exceeds a threshold distance value, for each object in memory in which said character occurs at a position in the sequence of the characters of said object corresponding to the position of said contact location in said input sequence, said object is ranked by the word evaluation component as an object that is excluded from presentation to the user for selection. One or a plurality of the identified candidate groupings of the objects in memory comprise objects that are excluded from presentation to the user for selection, wherein at least one of the calculated distance values included in the calculated sum of distance values for each object in said one or identified candidate groupings of objects exceeds a threshold distance value. The auto-correcting keyboard region is separated into two or more predefined clustering regions, each of which contains the known locations of one or a plurality of characters, and wherein each objects in memory is assigned to a predefined group according to which of said two or more predefined clustering regions contain the known locations corresponding to one or a plurality of the initial characters of said object. In one embodiment, the auto-correcting keyboard region is separated into three predefined clustering regions, and wherein each object in memory is assigned to one of nine predefined groupings based which of the three predefined clustering regions contain the known locations corresponding to each of the first two characters of said object.

Preferably, for each character corresponding to a known location in the auto-correcting keyboard region, a region is predefined around one or a plurality of said known locations wherein the distance between an input contact location falling within said predefined region and the known character location within said predefined region is calculated as a distance of zero. Most preferably, the relative sizes of said predefined regions correspond to the relative frequencies of occurrence of the characters associated with the known locations within said predefined regions. The predefined region around the known location of a character corresponds to a displayed key on the touch screen. Further, at least one of the locations with known coordinates in the auto-correcting keyboard region corresponds to a plurality of characters, one or a plurality of which include various diacritic marks, wherein the plurality of characters comprise variant forms of a single base character, and wherein objects in memory are stored with their correct accented characters.

Preferably, the selection component presents the identified one or a plurality of candidate objects for selection by the user in a candidate object list in the text display area. Most preferably, the selection component identifies the highest ranked candidate object and presents the identified object in the candidate object list in the position nearest to the auto-correcting keyboard region. In addition, user selection of a character that is associated with a contact outside of the auto-correcting keyboard region accepts and outputs the determined highest ranked candidate object at a text insertion point in the text display area prior to outputting the selected character at the text insertion point in the text display area. The user selection of an object for output at a text insertion point in the text display area terminates the current input sequence such that the next contact within the auto-correcting keyboard region starts a new input sequence. In addition, the selection component detects a distinctive manner of selection that is used to select a candidate object, and wherein upon detecting that an object has been selected through said distinctive manner, the system replaces the current input sequence of actual contact locations with an input sequence of contact locations corresponding to the coordinate locations of the characters comprising the selected object, and wherein a next contact in the auto-correcting keyboard region is appended to the current input sequence.

Preferably, the word evaluation component determines, for each determined contact location in each input sequence of contact locations, the closest known location corresponding to a character, and constructs an exact typing object composed of said determined corresponding characters in the order corresponding to the input sequence of contact locations. Most preferably, for each input sequence of contact locations, the selection component presents said exact typing object to the user for selection. Further, when the user selects said exact typing object for output to the text display area on the output device and said exact typing object is not already included as one of the objects in memory, said exact typing object is added to the memory. Prior to displaying the exact typing object to the user for selection, the selection component compares the exact typing object to a database of offensive objects, each of which is associated with an acceptable alternative object for display, and if a match is found, replaces the exact typing object with the associated acceptable object for presentation to the user.

Preferably, the selection component identifies the highest ranked candidate object and presents the identified object at the text insertion point in the text display area on the output device. Most preferably, the text entry system includes a select key region associated with an object selection function, wherein when said select key region is contacted, the object presented at the text insertion point in the text display area on the output device is replaced with next highest ranked object of the identified one or a plurality of candidate objects.

Preferably, the text entry system includes a delete key region associated with a delete function, wherein when the current input sequence includes at least one contact and said delete key region is contacted, the last input contact from the current input sequence of contacts is deleted, without terminating the current input sequence. In another preferred embodiment, the text entry system includes an Edit Word key region associated with an Edit Word function, wherein when no current input sequence exists and said Edit Word key region is contacted:

(i) when the text insertion point in the text display area on the output device is contained within a previously output word, the system establishes a new current input sequence consisting of a sequence of contact locations corresponding to the coordinate locations associated with the characters of said word, and

(ii) when the text insertion point in the text display area on the output device is located between two previously output words, the system establishes a new current input sequence consisting of a sequence of contact locations corresponding to the coordinate locations associated with the characters of the word adjacent to the text insertion point, and wherein the text entry system processes said new current input sequence and determines a corresponding ranking of new candidate objects, and wherein selection of one of the new candidate objects replaces the previously output word used to establish said new current input sequence.

Preferably, as the user enters an input sequence by performing a sequence of contact actions within the auto-correcting keyboard region, the processor determines the location associated with each user contact action by recording each contact action in the sequence as an indexed primary set of a fixed number of two or more regularly spaced contact points along the path traced out by the user contact action, and by assembling two or more corresponding secondary sets of contact points by taking, for each of the two or more possible primary index values, the sequence of contact points having the same index value, one from each recorded indexed primary set of contact points, and by determining with respect to each word is selected by the user for output, a minimizing primary index value that identifies the assembled secondary set of contact points for which the calculated distance between the assembled secondary set of contact points and the known locations corresponding to the characters of the selected word is minimized, and whereby for a next input sequence of user contact actions, the distance value calculation component calculates distance values based on a sequence of contact locations determined as the secondary set of contact point locations assembled from said next input sequence of contact actions corresponding to the determined minimizing primary index value. Most preferably, for a plurality of user input sequences, the distance value calculation component computes a running average of the distance calculations for each of the two or more assembled secondary sets corresponding to the two or more primary index values, and whereby for a next input sequence of contact actions, the distance value calculation component calculates distance values based on a sequence of contact locations determined as the secondary set of contact point locations assembled from said next input sequence of contact actions corresponding to the minimizing primary index value determined with respect to said computed running averages. Further, for each primary index value, the distance value calculation component computes a running average of the horizontal and vertical components of the offset of the coordinate location corresponding to each character of each selected word with respect to the coordinate location of each corresponding recorded indexed contact point, and wherein in performing distance calculations for the word evaluation component, the distance value calculation component adjusts the horizontal and vertical coordinates of each recorded indexed contact point by an amount that is a function of the average horizontal and vertical offsets computed with respect to the corresponding primary index value.

Preferably, for each input contact location, the distance value calculation component computes a running average of the horizontal and vertical components of the offset of the coordinate location corresponding to each character of each selected word with respect to the coordinates of each corresponding input contact location, and wherein in performing distance calculations for the word evaluation component, the distance value calculation component adjusts the horizontal and vertical coordinates of each input contact location by amounts that are functions of the computed average signed horizontal and vertical offsets. Alternatively, the processor further comprises a stroke recognition component that determines for each user contact action within the auto-correcting keyboard region whether the point of contact is moved less than a threshold distance from the initial contact location prior to being lifted from the touch sensitive surface, whereby:

(a) when the point of contact is moved less than a threshold distance from the initial contact location prior to being lifted from the touch sensitive surface, the stroke recognition component determines that the user contact is a tap contact, and the location determined to be associated with the user contact is added to the current input sequence of contact locations to be processed by the distance value calculation component, the word evaluation component, and the selection component, and

b) when the point of contact is moved greater than or equal to a threshold distance from the initial contact location prior to being lifted from the touch sensitive surface, the stroke recognition component determines that the user contact is one of a plurality of stroke contacts that are associated with known system functions, and classifies the stroke contact as one of the plurality of predefined types of stroke contacts.

Preferably, when a threshold number of contact locations in the input sequence are further than a threshold maximum distance from the corresponding character in the sequence of characters comprising a given candidate object, said object is identified as no longer being a candidate object for the selection component. Alternatively, the processor further comprises a frequency promotion component for adjusting the frequency of use associated with each object in memory as a function of the number of times the object is selected by the user for output to the text display area on the output device. Moreover, the frequency of use associated with each object in memory comprises the ordinal ranking of the object with respect to other objects in memory, wherein an object associated with a higher relative frequency corresponds to a numerically lower ordinal ranking, and wherein when an object is selected for output by the user, the frequency promotion component adjusts the ordinal ranking associated with said selected object by an amount that is a function of the ordinal ranking of said object prior to said adjustment. Further, the function used by the frequency promotion component to determine the amount by which the ordinal ranking associated with a selected object is adjusted reduces said amount for objects with ordinal rankings that are associated with relatively higher frequencies of use. The frequency promotion component analyzes additional information files that are accessible to the text entry system to identify new objects contained in said files that are not included among the objects already in said memory of said text entry system, and wherein said newly identified objects are added to the objects in memory as objects that are associated with a low frequency of use. Further, the frequency of use associated with a newly identified object that is added to the objects in memory is adjusted by the frequency promotion component as a function of the number of times that the newly identified object is detected during the analysis of said additional information files.

Preferably, the processor further comprises a frequency promotion component for adjusting the frequency of use associated with each object in memory as a function of the number of times the object is selected by the user for output to the text display area on the output device with respect to other objects associated with the same predefined grouping. Most preferably, when an object is selected by the user for output to the text display area on the output device, the frequency promotion component increases the value of the frequency associated with the selected object by a relatively large increment, and decreases by a relatively small decrement the frequency associated with unselected objects that are associated with the same grouping as the selected object. Alternatively, information regarding the capitalization of one or a plurality of objects is stored along with the objects in memory and wherein the selection component presents each identified object in a preferred form of capitalization according to the stored capitalization information. In another embodiment, one or a plurality of objects in memory are associated with a secondary object in memory comprising a sequence of one or a plurality of letters or symbols, and wherein when the selection component identifies one of said objects for presentation to the user based on the matching metric calculated by the word evaluation component, the selection component presents the associated secondary object for selection.

The present invention further provides a text entry system comprising:

(a) a user input device comprising a keyboard constructed with mechanical keys including an auto-correcting keyboard region comprising a plurality of keys, each corresponding to a character of an alphabet and each at a known coordinate location, wherein each time a user activates one or a plurality of adjacent keys in the auto-correcting keyboard region within a predetermined threshold period of time to generate a key activation event, a determined location corresponding to the key activation event is appended to a current input sequence of the determined locations of the key activation events;

(b) a memory containing a plurality of objects, wherein each object is a string of one or a plurality of characters forming a word or a part of a word, wherein each object is further associated with a frequency of use;

(c) an output device with a text display area; and

(d) a processor coupled to the user input device, memory, and output device, said processor comprising:

(i) a distance value calculation component which, for each generated key activation event location in the input sequence of key activation events, calculates a set of distance values between the key activation event location and the known coordinate locations corresponding to one or a plurality of keys within the auto-correcting keyboard region;

(ii) a word evaluation component which, for each generated input sequence, identifies one or a plurality of candidate objects in memory, and for each of the one or a plurality of identified candidate objects, evaluates each identified candidate object by calculating a matching metric based on the calculated distance values and the frequency of use associated with the object, and ranks the evaluated candidate objects based on the calculated matching metric values; and

(iii) a selection component for identifying one or a plurality of candidate objects according to their evaluated ranking, presenting the identified objects to the user, and enabling the user to select one of the presented objects for output to the text display area on the output device.

Preferably, (a) each of the plurality of objects in memory is further associated with one or a plurality of predefined groupings of objects; and (b) the word evaluation component, for each generated input sequence, limits the number of objects for which a matching metric is calculated by identifying one or a plurality of candidate groupings of the objects in memory, and for one or a plurality of objects associated with each of the one or a plurality of identified candidate groupings of objects, calculates a matching metric based on the calculated distance values and the frequency of use associated with each candidate object, and ranks the evaluated candidate objects based on the calculated matching metric values. Further, the keys associated with the characters of the alphabet are arranged in the auto-correcting keyboard region in approximately a standard "QWERTY" layout.

Preferably, when a key activation event is detected comprising the simultaneous activation of a plurality of adjacent keys in the auto-correcting keyboard region, a location corresponding to said key activation event is determined as a function of the locations of the simultaneously activated keys, and said determined location is appended to the current input sequence of the locations of the key activation events. Most preferably, the function used to determine the location of said key activation event comprises the computation of the location corresponding to the center of the locations of the simultaneously activated keys. Further, the function used to determine the location of said key activation event comprises the computation of the location corresponding to the weighted center of gravity of the locations of the simultaneously activated keys, wherein the weights associated with each of the keys in the auto-correcting keyboard region correspond to the relative frequencies of occurrence of the characters associated with the keys, wherein said relative frequencies are determined with respect to the frequencies of occurrence of the characters in the objects in memory.

Preferably, when a key activation event is detected comprising the activation of a plurality of adjacent keys in the auto-correcting keyboard region within a predetermined threshold period of time, wherein at all times during said key activation event at least one of said plurality of adjacent keys is activated and wherein at any moment during said key activation event that any subset of said plurality of keys is simultaneously activated, said simultaneously activated subset of keys comprises keys that are contiguously adjacent, a location corresponding to said key activation event is determined as a function of the locations of the entire plurality of adjacent keys detected during said key activation event, and said determined location is appended to the current input sequence of the locations of the key activation events. Most preferably, the function used to determine the location of said key activation event comprises the computation of the location corresponding to the center of the locations of the simultaneously activated keys. Further, the function used to determine the location of said key activation event comprises the computation of the location corresponding to the weighted center of gravity of the locations of the simultaneously activated keys, wherein the weights associated with each of the keys in the auto-correcting keyboard region correspond to the relative frequencies of occurrence of the characters associated with the keys, wherein said relative frequencies are determined with respect to the frequencies of occurrence of the characters in the objects in memory.

Preferably, the auto-correcting keyboard region includes one or a plurality of keys associated with one or a plurality of punctuation characters, wherein said memory includes one or a plurality of objects in memory which include one or a plurality of the punctuation characters associated with keys in said auto-correcting keyboard region. Alternatively, the word evaluation component calculates the matching metric for each candidate object by summing the distance values calculated from determined location in the input sequence to the known location of the key corresponding to the character in the corresponding position of the candidate object, and applying a weighting function according to the frequency of use associated with the object. In another embodiment, at least one of the keys in the auto-correcting keyboard region corresponds to a plurality of characters, one or a plurality of which include various diacritic marks, wherein the plurality of characters comprise variant forms of a single base character, and wherein objects in memory are stored with their correct accented characters.

Preferably, the selection component presents the identified one or a plurality of candidate objects for selection by the user in a candidate object list in the text display area. Most preferably, the selection component identifies the highest ranked candidate object and presents the identified object in the candidate object list in the position nearest to the auto-correcting keyboard region. Further, activation of a key that is associated with a character, wherein the key is not included within the auto-correcting keyboard region, accepts and outputs the determined highest ranked candidate object at a text insertion point in the text display area prior to outputting the selected character at the text insertion point in the text display area. Further, the user selection of an object for output at a text insertion point in the text display area terminates the current input sequence such that the next key activation event within the auto-correcting keyboard region starts a new input sequence.

The present invention further provides a process for auto-correcting text entry system comprising:

(a) providing a user input device comprising a touch sensitive surface including an auto-correcting keyboard region comprising a plurality of the characters of an alphabet, wherein each of the plurality of characters corresponds to a location with known coordinates in the auto-correcting keyboard region, wherein each time a user contacts the user input device within the auto-correcting keyboard region, a location associated with the user contact is determined and the determined contact location is added to a current input sequence of contact locations;

(b) providing a memory containing a plurality of objects, wherein each object is a string of one or a plurality of characters forming a word or a part of a word, wherein each object is further associated with a frequency of use;

(c) providing an output device with a text display area; and

(d) providing a processor coupled to the user input device, memory, and output device, said processor comprising:

(i) a distance value calculation component which, for each determined contact location in the input sequence of contacts, calculates a set of distance values between the contact locations and the known coordinate locations corresponding to one or a plurality of characters within the auto-correcting keyboard region;

(ii) a word evaluation component which, for each generated input sequence, identifies one or a plurality of candidate objects in memory, and for each of the one or a plurality of identified candidate objects, evaluates each identified candidate object by calculating a matching metric based on the calculated distance values and the frequency of use associated with the object, and ranks the evaluated candidate objects based on the calculated matching metric values; and

(iii) a selection component for (a) identifying one or a plurality of candidate objects according to their evaluated ranking, (b) presenting the identified objects to the user, enabling the user to select one of the presented objects for output to the text display area on the output device.

Preferably, the selection component further comprises (c) resetting the current input sequence of the locations of the points of contact to an empty sequence upon detecting the selection by the user of one of the presented objects for output to the text display area on the output device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic view of a preferred embodiment of a portable computer incorporating a reduced keyboard system of the present invention which automatically corrects input keystrokes; FIG. 1B is the same schematic view showing an embodiment of a word choice list that is displayed after the user has entered a sequence of keystrokes within the auto-correcting keyboard region.

FIG. 2 is a hardware block diagram of the reduced keyboard system of FIGS. 1A and 1B.

FIG. 3 is a schematic view of a preferred embodiment of an auto-correcting keyboard region of the reduced keyboard system of the present invention which automatically corrects input keystrokes, showing its division into three clustering regions and three example contact points.

FIGS. 4A through 4K show a flow chart of a preferred embodiment of software to determine the intended text to be generated in response to an input sequence of keystrokes.

FIGS. 5A through 5E are schematic views showing a sequence of character inputs as an illustrative example of entering a word on a preferred embodiment of a portable computer incorporating a reduced keyboard system of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Since user keystroke entries are presumed to be possibly inaccurate, there is some ambiguity as to how a particular sequence of keystrokes should be interpreted in order to generate the sequence of characters that the user intended to type. The present invention provides a process and system (i.e., apparatus or device having the inventive software within) wherein the user is presented with one or more alternate interpretations of each keystroke sequence corresponding to a word such that the user can easily select the desired interpretation, and wherein no special action need be taken to select the interpretation deemed most likely. This approach enables the system to utilize the information contained in the entire sequence of keystrokes corresponding to a word in resolving what the user's likely intention was for each character of the sequence.

The method of the present invention has two very significant advantages over prior systems, such as that disclosed by U.S. Pat. No. 5,748,512. One is that the inventive system is able to utilize information regarding both preceding and succeeding keystrokes in determining the intended character for each keystroke, together with the length of the word and a database that includes information as to the relative frequencies of potentially matching words. This is far more information than can be utilized by prior systems, and greatly increases the performance of the system. The second advantage is that the user need only interact and respond to predictions by the system at word boundaries, after all the characters of each word have been entered, rather than having to examine, and accept or reject each character generated by the system immediately following each keystroke. This greatly enhances the usability of the system, since the user is thus able to focus much more on the entry of text on the keyboard without needing to constantly divert his attention to the display following each keystroke. Another advantage is the system also accommodates punctuation characters such as a hyphen or apostrophe that are commonly embedded in words such as hyphenated compounds and contractions in English. Such embedded punctuation characters can be associated with one or more keys or character locations included among those associated with alphabetic characters.

Definitions

"Keyboard" shall mean include any input device having defined areas including, but not limited to, a touch sensitive screen having a defined area containing a plurality of defined locations associated with characters, a touch sensitive screen having defined areas for keys, discrete mechanical keys, or membrane keys.

"Auto-correcting keyboard region" refers to that region of the keyboard having the inventive auto-correcting process and features applied.

"Object" shall mean a string of one or more characters forming a word or part of a word, including without limitation, wordstems, prefixes and suffixes.

"Word" shall mean a string of one or more characters that is used in a given language, also including without limitation acronyms, abbreviations and proper nouns.

"Wordstem" shall mean a "root word" or "root stem." For example, the word "interestingly" consists of the root word "interest" to which the suffix "ingly" has been appended. As a further example, the word "surprisingly" consists of the root stem "surpris" to which the suffix "ingly" has been appended.

"Module" is a logical organization of objects based upon characteristics of the objects. For example, (1) words of the French language versus words of the English language are arranged in different modules, (2) a verb stem module contains verb stems to each of which one or more possible suffixes may be appended, wherein the suffixes are contained in one or more suffix modules associated with the verb stem module, wherein the suffixes from the suffix modules can be appended to a verb stem in the verb stem module to form a properly inflected word.

A "contact action" comprises the entirety of a user action which results in a contact with the keyboard, starting from the first point and moment of contact, and including any additional contiguous points of contact that are detected up to the moment at which contact with the keyboard is terminated. Examples of contact actions include, but are not limited to, physically touching a touch sensitive screen with a stylus or finger and moving the stylus or finger to a greater or lesser degree prior to lifting the stylus or finger from the screen, or moving a mouse cursor to position it within a displayed keyboard region and clicking the mouse button then moving the mouse cursor to a greater or lesser degree prior to releasing the mouse button.

A "contact location" is the location determined to correspond to a user action which results in a contact with the keyboard. Methods of determining a contact location include, but are not limited to, detecting the point on a touch screen or similar device where the initial or final contact was made by the user, or detecting a user action such as a mouse click whereby the contact location is determined corresponding to the location of the mouse cursor within a displayed keyboard region at the time of that the mouse button is first depressed.

A "distance value calculation component" calculates a set of distance values between a contact location and the known coordinate locations corresponding to one or more characters within the auto-correcting region of the keyboard. The method used to calculate the distance between two locations includes, but is not limited to, assigning Cartesian coordinates to each location and calculating the distance between two locations according to standard Cartesian coordinate distance analysis, assigning Cartesian coordinates to each location and calculating the distance between two locations as the square of the standard Cartesian coordinate distance, and assigning Cartesian coordinates to each location and calculating the distance between two locations according to Cartesian coordinate distance analysis where the vertical component is adjusted by a weighting factor.

A "matching metric" is a score calculated for an object with respect to an input sequence of contact locations as a means to estimate how likely it is that the object corresponds to the user's intention in performing the input sequence of contacts. For example, a matching metric can be calculated in one embodiment as the sum of the squares of the distances from each contact location in the entry sequence to the location assigned to the character in the corresponding position of a given candidate object, and then multiplying the sum of the squared distances by a frequency adjustment factor, which in one preferred embodiment is calculated as the base 2 logarithm of the ordinal position of the word with respect to other potential candidate objects, where objects associated with higher relative frequencies correspond to lower ordinal positions (i.e., the most frequent object is at position "1"). Thus, in this embodiment, the lower the numeric value of the calculated matching metric, the more likely a given object is deemed to correspond to the user's intention in generating a sequence of contact points.

An "evaluated ranking" is the relative prioritization of a set of candidate objects according the likelihood that each of the objects corresponds to the user's intention in generating a sequence of contact points, where this likelihood is determined according to the matching metric calculated for the objects.

A "key activation event" includes but is not limited to an event that comprises the entirety of the activated keys detected during the course of a user action which results in the activation of one or more adjacent keys of a mechanical keyboard, starting from the first depressed key and including the time at which it was depressed, and including any additional keys that are adjacent to the first depressed key and that are simultaneously depressed, detected up to the moment at which neither the first key nor any simultaneously depressed adjacent key is depressed.

With regard to FIG. 1A, a reduced auto-correcting keyboard system 100 formed in accordance with the present invention is depicted incorporated in a palmtop portable computer 102. Portable computer 102 contains a reduced keyboard 105 implemented on a touch screen display 103, which is used to generate text to be output to text display region 104. For purposes of this application, the term "keyboard" is defined broadly to include any input device having defined areas including, but not limited to, a touch screen having defined areas for keys, discrete mechanical keys, or membrane keys. Keyboard 105 has an auto-correcting keyboard region 106 wherein the 26 letters of the English alphabet plus an apostrophe are displayed in approximately the standard "QWERTY" arrangement. In this preferred embodiment, it is relevant to note that the aspect ratio of the keyboard 106 (the ratio of its width to its height) is less than 2:1, whereas for a standard computer keyboard or typewriter, this ratio is approximately 4:1. This aspect ratio renders the keyboard 106 easier to use in that the less elongated shape tends to minimize the distance the stylus must be moved between letters at opposite ends of the keyboard, while enhancing the system's ability to distinguish between letters in adjacent rows by increasing their relative separation. This makes it easier for the user to contact the keyboard in a location that is relatively close to the intended letter in the vertical dimension. Consequently, in a preferred embodiment, the distance of a contact point from a letter is calculated using a method that increases the relative weight of the vertical component of the distance with respect to the horizontal component.

The keyboard may be of any size, very small or very large. For example, an implementation using a space for the auto-correcting keyboard as small as 1 cm by 0.5 cm that includes all 26 letters of the English alphabet has been found to be quite usable with a small plastic stylus. When embodied as a keyboard of this size, a well-known key arrangement such as the standard "QWERTY" layout may be used. With this key arrangement it is not necessary to include legible displayed characters, because the relative locations of each character in the defined keyboard space are well known to users familiar with such a standard layout. Alternatively, a very small label such as a dot may be displayed at each character location to aid the user.

In accordance with another aspect of the invention, the internal, logical representation of the characters need not mirror the physical arrangement represented by the labels on the actual characters in the auto-correcting keyboard. For example, in a database constructed to represent a French vocabulary module, the accented characters A and A may also be associated with the unaccented character A that appears as an explicitly labeled key in a mechanical keyboard or character location in a keyboard implemented on a touch-sensitive display screen. The word entries in the French vocabulary module include the necessary information to determine whether a given word is spelled with an accented or unaccented character so that the correctly spelled form can be automatically generated based on an input contact point sufficiently near the key or character location associated with the unaccented character. This is a significant advantage for languages such as French that often use accented characters since no special typing techniques, additional keys, or additional keystrokes are required to type words using their correct spellings including appropriate accents.

The preferred keyboard of FIG. 1A contains six additional keys associated with the execution of specific functions or the generation of specific characters. These keys include a Shift key 108, a Space key 110, a BackSpace key 112, an Edit Word key 114, a Symbols Mode key 116, a Return (or "Enter") key 118, an Alternate Keyboard Mode key 120, and a Numeric Mode key 122. The function of these keys will be discussed in conjunction with FIG. 1B.

Text is generated using the keyboard system via keystrokes on the auto-correcting keyboard 106. As a user enters a keystroke sequence using the keyboard, text is displayed on the computer display 103. Two overlapping regions are defined on the display each of which display information to the user. An upper output text region 104 displays the text entered by the user and serves as a buffer for text input and editing. A word choice list region 150, which in a preferred embodiment shown in FIG. 1B is super-imposed on top of the text region 104, provides a list of words and other interpretations corresponding to the keystroke sequence entered by a user. The word choice list region 150 aids the user in correcting inaccuracies in the entered keystrokes. In another embodiment, the system may be implemented on a device with limited display space, and display only the Default or most likely word object at the insertion point 107 in the text being generated.

In another preferred embodiment, the keyboard of the present invention is implemented using a keyboard device. Examples of such devices would include the standard desktop keyboard used with personal computers, or much smaller mechanical keyboards such as those commonly used in portable, hand-held electronic devices such as two-way pagers that, in the case of English and other Latin-alphabet based languages, include a full set of at least 26 small, closely spaced keys, often arranged in the standard "QWERTY" layout. This embodiment is logically identical to a touch screen implementation in which the points at which physical contact with the screen can be detected correspond exactly to the set of coordinates associated with the characters of the keyboard. Thus, the methods of the present invention may be applied equally well to such mechanical keyboard implementations.

However, mechanical keyboards have a distinguishing characteristic from touch screens in that a single inaccurate or erroneous key activation may not only consist of activating a key other than the one intended, but also may consist of simultaneous or closely sequential activation of two or more adjacent keys, wherein the activated keys may or may not include among them the intended key. Thus, in accordance with another aspect of the invention, a sequence of keystrokes on the auto-correcting keyboard is filtered through a window of both time and space, in that a single intended keystroke may activate more than one adjacent key. An example is when a user depresses 2, 3 or 4 keys when the user's finger is not properly aligned with the intended key or any single specific key. Thus, following each received keystroke, the keystroke is not processed until after the system waits for a very brief timeout threshold, or until a keystroke is received on a non-adjacent key. If the next keystroke occurs on an adjacent key, or if multiple keystrokes occur on adjacent keys, before the expiration of the timeout threshold, the detected keys are regarded as a single keystroke event. In such cases, a "virtual" point of contact is calculated at the center of the set of "simultaneously" activated keys. The distances from this calculated "virtual" contact point and the known character locations (key locations in this case of a mechanical keyboard) are calculated by interpolating to a logical coordinate frame with a finer resolution than that of the physical sensors (keys).

In another embodiment of the invention, keystrokes on the auto-correcting keyboard are not matched to characters in isolation, but rather entire sequences of keystrokes corresponding to completed words are matched against a lexicon of candidate words that includes information regarding the relative frequency with which each word appears in a representative corpus of usage. In this way, the system is often able to correctly compensate for occasional keystroke errors of a larger than average magnitude, or even multiple errors of a relatively larger magnitude when the intended word is of high relative frequency. This word-level analysis of keystroke input sequences are a key factor in enabling the inventive system to flexibly accommodate user keystroke errors.

The word-level analysis of keystroke sequences enables the system to generate punctuation characters such as a hyphen or apostrophe that are commonly embedded in words such as hyphenated compounds and contractions in English. Such embedded punctuation characters can be associated with one or more keys or character locations included in the auto-correcting keyboard among those associated with alphabetic characters. When more than one punctuation character is associated with a single key, the specific punctuation character intended can be disambiguated based on the information included in the lexicon. Thus, for example, if a word in the lexicon includes an apostrophe in a position corresponding to a key contact in the region of an ambiguous punctuation key, the matching algorithm will automatically identify the associated word and disambiguate the keystroke as an apostrophe. Simultaneously, the system can separately analyze the keystroke sequences preceding and following the key contact in the region of the punctuation key to determine the most likely matching words in the lexicon and calculate the likelihood that a hyphenated compound was intended. In the case of a keyboard implemented on a touch-sensitive display screen, other symbols, numbers or other characters not commonly used are relegated to a separate symbol selection scheme, preferably through presentation in a series of temporarily displayed tables. Such Symbol Tables are preferably accessed through a function key or touch entry element assigned adjacent to the auto-correcting keyboard region. In the case of a mechanical keyboard, these other symbols, numbers and uncommon characters are often accommodated through additional keys not included in the auto-correcting keyboard.

In accordance with another aspect of the invention, candidate words that match the input sequence are presented to the user in a word selection list on the display as each input is received. In accordance with another aspect of the invention, the word interpretations are presented in the order determined by the matching metric calculated for each candidate word, such that the words deemed to be most likely according to the matching metric appear first in the list. Selecting one of the proposed interpretations of the input sequence terminates an input sequence, so that the next keystroke inside the auto-correcting keyboard region starts a new input sequence. In accordance with yet another aspect of the invention, only a single word interpretation appears on the display, preferably at the insertion point for the text being generated. The word interpretation displayed is that deemed to be most likely according to the matching metric. By repeatedly activating a specially designated selection input, the user may replace the displayed word with alternate interpretations presented in the order determined by the matching metric. An input sequence is also terminated following one or more activations of the designated selection input (effectively selecting exactly one of the proposed interpretations of the sequence for actual output by the system), so that the next keystroke inside the auto-correcting keyboard region starts a new input sequence.

In accordance with another aspect of the invention, for each input sequence of contact points, a word is constructed by identifying the character nearest each contact point and composing a word consisting of the sequence of identified characters. This "Exact Type" word is then presented as a word choice in the word selection list. This word may then be selected in the usual manner by, for example, touching it in the word selection list. Exact Type entries can be edited by, for example, pressing a backspace key to delete one character at a time from the end of the word. Once the user selects the Exact Type word, it is automatically "accepted" for output and is added to the information being composed. When so selected, the Exact Type string may be added as a candidate for inclusion into the lexicon of words so that in the future it can be typed using the auto-correcting keyboard without needing to precisely contact each letter of the word as is necessary in first entering an Exact Type entry.

FIG. 1B shows a preferred embodiment of a word choice list 150 that is displayed after the user has entered a sequence of keystrokes within the auto-correcting keyboard region 106. The word choice list includes a Cancel key 152, wherein contacting the Cancel key causes the system to discard the current input sequence, clearing the word choice list and causing the system to restore the display of any text or graphics obscured by the appearance of the word choice list. The "Exact Type" word 154 shows the sequence of letters closest to the actual contact points of the input sequence, whether or not these correspond to any word in any vocabulary module. In the example shown in FIG. 1B, the Exact Type word "rwzt" does not correspond to an English word. In a preferred embodiment, selecting the Exact Type word for output results in the automatic addition of that word to the appropriate vocabulary module if it is not already included. The Default word 160 ("text" in the example of FIG. 1B) is the word from the vocabulary modules determined to have the lowest value of the matching metric (that is, the more likely the word corresponds to the user's intention), and in a preferred embodiment, is shown at the bottom of the word choice list, nearest to the auto-correcting keyboard region 106. Similarly, three alternate word choices 157 are shown in the list in an order determined by their corresponding matching metric values.

The Symbols Mode key 116, the Alternate Letter Mode key 120, and the Numeric Mode key 122 each cause a corresponding keyboard of punctuation and symbols, alphabetic letters, and numeric digits, respectively, to appear on the display screen. The user can then select the desired character or characters from the displayed keyboard. If a word choice list was displayed prior to displaying such an alternate keyboard, the selection of any character from the displayed alternate keyboard causes the Default word of the previously displayed word choice list to be output to the output text region 104 prior to outputting the selected character from the alternate keyboard. Similarly, if a word choice list was displayed prior to contacting the Space key 110 or the Return key 118, the Default word 160 is flushed to the output text region 104 prior to generating a single space or carriage return character, respectively.

In the preferred embodiment, the Shift key 108 functions as a latching Shift key, such that contacting it causes the letter associated with the next contact in the auto-correcting keyboard 106 to be generated as an upper-case letter. In another preferred embodiment, two successive contacts on the Shift key 108 puts the system in "Caps-Lock," and a subsequent activation cancels "CapsLock" mode. BackSpace key 112 deletes the last input contact from the current sequence of contacts if one exists, and otherwise deletes the character to the left of the cursor at the insertion point 107 in the output text region 104. When no current input sequence exists, a contact on the Edit Word key 114 causes the system to establish a current input sequence consisting of the coordinate locations associated with the letters of the word that contains the insertion point cursor 107 or is immediately to the left of this cursor in the output text region 104. The result is that this word is "pulled in" to the system creating a word choice list in which the word appears both as the Default word 160 and the Exact Type word 154.

A block diagram of the reduced keyboard disambiguating system hardware is provided in FIG. 2. The touch screen 202 and the display 203 are coupled to a processor 201 through appropriate interfacing circuitry. Optionally, a speaker 204 is also coupled to the processor. The processor 201 receives input from the touch screen, and manages all output to the display and speaker. Processor 201 is coupled to a memory 210. The memory includes a combination of temporary storage media, such as random access memory (RAM), and permanent storage media, such as read-only memory (ROM), floppy disks, hard disks, or CD-ROMs. Memory 210 contains all software routines to govern system operation. Preferably, the memory contains an operating system 211, auto-correction software 212, and associated vocabulary modules 213 that are discussed in additional detail below. Optionally, the memory may contain one or more application programs 214, 215, 216. Examples of application programs include word processors, software dictionaries, and foreign language translators. Speech synthesis software may also be provided as an application program, allowing the reduced auto-correcting keyboard system to function as a communication aid.

In accordance with another aspect of the invention, each input sequence is processed with reference to one or more vocabulary modules, each of which contains one or more words together with information about each word including the number of characters in the word and the relative frequency of occurrence of the word with respect to other words of the same length. Alternatively, information regarding the vocabulary module or modules of which a given word is a member is stored with each word. Each input sequence is processed by summing the distances calculated from each contact point in the entry sequence to the location assigned to the letter in the corresponding position of each candidate word, wherein the distances are calculated according to one of the preferred methods. This total distance is combined with the frequency information regarding each candidate word to calculate a matching metric by which the various candidate words are rank ordered for presentation to the user. In one preferred embodiment, the matching metric is calculated as follows. The square of the distance from each contact point in the entry sequence to the location assigned to the letter in the corresponding position of each candidate word is calculated, and the sum of the squared distances is calculated for each candidate word. This sum is then multiplied by a frequency adjustment factor, which in one preferred embodiment is calculated as the base 2 logarithm of the ordinal position of the word in the candidate list, where words of higher relative frequency are moved "higher" in the list to positions corresponding to a lower ordinal position (i.e., the most frequent word is at position "1"). Thus, the lower the numeric value of the calculated matching metric, the more likely a given word is deemed to correspond to the user's intention in generating a sequence of contact points.

In another aspect of the invention, prior to multiplying the sum of the distances (from each contact point in the entry sequence to each corresponding letter in a candidate word) by the frequency adjustment factor, a fixed increment is added to the sum so that it is at least greater than or equal to this increment value. This is done to avoid calculating a matching metric value of zero (i.e., the most likely match) when the sequence of contact points happens to correspond exactly to the spelling of a given word, even when that word occurs with very low frequency (i.e., has a high numeric ordinal position). This allows much more frequently occurring words to produce a better matching metric even when an inaccurate sequence of contact points is entered. In one implementation of this preferred embodiment, it was found that a fixed increment value of approximately twice the average distance between adjacent characters in the keyboard was effective in reducing spurious matches with infrequent words.

In accordance with another aspect of the invention, words in each vocabulary module are stored such that words are grouped into clusters or files consisting of words of the same length. Each input sequence is first processed by searching for the group of words of the same length as the number of inputs in the input sequence, and identifying those candidate words with the best matching metric scores. In accordance with another aspect of the invention, if fewer than a threshold number of candidate words are identified which have the same length as the input sequence, and which have a matching metric score better than a threshold value, then the system proceeds to compare the input sequence of N inputs to the first N letters of each word in the group of words of length N+1. This process continues, searching groups of progressively longer words and comparing the input sequence of N inputs to the first N letters of each word in each group until the threshold number of candidate words are identified. Viable candidate words of a length longer than the input sequence may thus be offered to the user as possible interpretations of the input sequence, providing a form of word completion. In another aspect of the invention, prior to multiplying the sum of the distances (from each contact point in the entry sequence to each corresponding initial letter in a candidate word whose length is greater than the length of the current input sequence) by the frequency adjustment factor, a second fixed increment is added to the sum so that it is greater than the distance sum that would be calculated for a word whose length corresponds exactly to the length of the current input sequence. This is done to assign a relatively higher matching probability to words whose length does correspond exactly. In another preferred embodiment, this second increment factor is a function of the difference in length between the candidate word and the current input sequence.

In accordance with another aspect of the invention, in order to increase the efficiency with which the vocabulary modules can be processed, each character mapped onto the touch-sensitive pad in the auto-correcting keyboard region is assigned a boundary of exclusion. Each such boundary identifies the region beyond which the distance from the contact point to the character will not be calculated and the character will be removed from consideration for that contact point in the input sequence, reducing the computation required by the distance calculation process. The boundaries of exclusion for several characters may share some or all common boundary segments. Examples of shared boundaries include the extreme edge of the auto-correcting keyboard region, or gross boundaries drawn through the character space to subdivide the auto-correcting keyboard into 2, 3 or more major clustering regions. Conceptually, it is identical to consider the boundary of exclusion for a given contact point, where any character outside that boundary is excluded from consideration as a match for that input point. For example, FIG. 3 shows an auto-correcting keyboard region 300 that consists of a horizontal rectangle which is divided vertically into three clustering regions 301, 302, 303 of approximately equal size, where these regions are defined such that each character falls into only one of the three clustering regions. The clustering regions are defined such that for each contact point in the auto-correcting keyboard region, at least one and frequently two of the three regions lie completely outside the boundary of exclusion for that contact point. For example, a contact point 311 at the left side of region 301 is far enough away from region 302 that all characters in region 302 (and region 303) could be defined to lie outside the boundary of exclusion for contact point 311. In contrast, the boundary of exclusion for contact point 312 at the right side of region 301 would extend into region 302 such that one or more characters in region 302 would be considered to lie inside the boundary, so that the only region completely outside the boundary of exclusion for contact point 312 would be region 303. The boundary of exclusion for contact point 313 in the center of region 302 could be considered to be far enough away from both region 301 and region 303 that all characters in both these regions could be defined to lie outside the boundary.

Such clustering regions are then used to increase the efficiency with which the system can identify the most likely matching words in one or more vocabulary modules for a given input sequence of contact points. Continuing the example described above and depicted in FIG. 3, the words of a given length in each vocabulary module can be divided up into nine different subgroups based on the clustering regions in which each of the first two letters of each word is found, since there are nine possible ordered pairs of such regions. Note that processing words of only one letter need not be optimized since very little calculation is required and there are only a very small number of one-letter words, even when every letter is treated as if it is a one-letter "word." For each of the first two contact points, letters in one or two of the clustering regions can be eliminated from consideration, so that all of the words in the sub-groups associated with letters in the eliminated regions can be skipped over without needing to perform any distance calculations. Thus, assuming a more or less equal distribution of total character frequency among the three regions for the first two character positions of words in the vocabulary modules, upon the receipt of the second contact point, the system need only calculate distances for and compare at most 4/9 of the candidate words (when only one clustering region is eliminated from consideration for each contact point) to as few as 1/9 of the candidate words (when two clustering regions are eliminated for each contact point). As would be obvious to one of ordinary skill in the art, this method can be used with a greater or lesser number of clustering regions, and for different numbers of initial contact points, with corresponding results. For example, four clustering regions could be used to divide candidate words into sixteen sub-groups based on the first two contact points.

In another embodiment of the invention, a subset of characters or functions will be associated with uniquely defined regions or keys outside the auto-correcting keyboard, where entries within these regions are interpreted as explicit entries of a specific character or function, for example, a Space key that unambiguously generates a single space when selected. For a defined set of such keys, selecting such a key immediately following an input sequence, and prior to performing an explicit selection of any of the interpretations offered by the system for the input sequence, results in the automatic acceptance of the interpretation of the input sequence deemed to be most likely according to the matching metric calculated for each candidate word. The input sequence is terminated, so that the next keystroke inside the auto-correcting keyboard region starts a new input sequence. Once the desired word interpretation of an input sequence has been determined and the sequence is terminated, the system automatically outputs the word so that it is added to the information being constructed. In the case of certain functions, for example the backspace function, an entry within the associated region is interpreted as an explicit entry of the backspace function, which is immediately executed. The result in this case however, does not terminate the input sequence, but simply deletes the last (most recent) input from the sequence. In general, keys outside the auto-correcting keyboard are immediately interpreted and acted upon according to the unique character or function associated with the key. Depending on the associated character or function, in some cases the current input sequence is terminated as a result.

In accordance with another aspect of the invention, the system distinguishes between two different types of contact events that occur in the area of the touch screen or touch-sensitive display that is used to display the auto-correcting keyboard region and other uniquely defined regions or keys outside the auto-correcting keyboard. One type of contact consists of a "tap" event, wherein the touch screen is contacted and then the contact is terminated without moving beyond a limited distance from the initial point of contact. This type of event is processed as a keystroke intended for the reduced auto-correcting keyboard system as described in this disclosure. The second type of contact consists of a "stroke" event, wherein the touch screen is contacted then the point of contact is moved in one or more directions beyond the limited distance threshold used to define a tap event. This second type of contact can then be processed by using a stroke recognition system using techniques that are well known in the art. This allows a number of additional functions or special characters to be made easily accessible to the user without having to trigger pull-down menus or define additional keys that would either require additional screen space or reduce the size of the keys provided. The interpretation of such strokes and the resulting character or function associated with a recognized stroke is then processed by the system in the same fashion as an activation of one of the uniquely defined regions or keys outside the auto-correcting keyboard. In this way, only a limited area of the available touch screen or touch-sensitive display needs to be used to accommodate both keyboard-based and stroke recognition input approaches.

In accordance with another aspect of the invention, the system performs additional processing of "tap" events to dynamically adjust to a particular user's style of contacting the touch screen or touch-sensitive display. For a user who contacts the display with a stylus "gesture" that closely approximates a point (i.e., the stylus contacts the display and is lifted before being moved any appreciable distance), there is no significant ambiguity as to where the user intended to contact the keyboard. However, when the stylus moves to a greater or lesser extent before being lifted from the display, there is ambiguity as to which point contacted during the duration of the stylus "gesture" best represents the point that the user intended to contact--the initial point of contact, the final point where the stylus was lifted, or some other point along the path of contact of the stylus. In a preferred embodiment, the system records the path traced out by each contact as a set of N contact points that include the endpoints of the path of contact and zero or more points equally spaced points along the path. For example, in an embodiment where N is set to 3, the set would include the endpoints and the midpoint of the path. Initially, one point of each set of recorded points is designated as the coordinate to be used to represent the point of contact in calculating distances to letters in the auto-correcting keyboard. For example, in a preferred embodiment, the initial point of contact recorded in each set is designated as the coordinate to be used to represent the point of contact in all distance calculations. Each time a word is selected for output from the word choice list, the distance calculation is repeated from each letter in the chosen word to each of the other sets of recorded points. For example, when N is set to 3 and the calculation is performed for the starting point of contact, the calculation is repeated for the set of midpoints and for the set of endpoints. Whichever set of points results in the minimum calculated distance is then designated as the set of points whose coordinates are to be used to represent the sequence points of contact in all subsequent distance calculations in creating the word choice list for each sequence of contacts. In another preferred embodiment, a running average is computed of the distance calculations performed for each point set, and the point set for which this running average is lowest is used for distance calculations in creating the word choice list. In another preferred embodiment, the running average is computed of the horizontal and vertical signed offset of the designated points from the intended target letters, and the coordinates used in distance calculations for creating the word choice list are adjusted by this average signed offset, or by a fixed fraction of this offset. Thus, if a user consistently contacts the touch screen somewhat to the left and below the intended letters, the system can automatically adjust and more accurately predict the intended word on average.

In accordance with another aspect of the invention, each character mapped onto the touch-sensitive pad in the auto-correcting keyboard region is assigned a region of territory. Each such region identifies an area wherein the distance from the user entry to the character is assigned the value of zero, simplifying the distance calculation process. The size of such regions can vary for different characters and functions. For example, a larger region may be assigned to a character that occurs with a relatively higher frequency within a representative corpus of usage. In one embodiment, this region assigned to a character simply corresponds to a defined key that is clearly circumscribed and demarcated on the touch screen, and to which the character is assigned.

The operation of the reduced auto-correcting keyboard system is governed by the auto-correction software 212 which is based in part on the distance between the contact point and the various candidate characters. In one embodiment of the invention, each character in the auto-correcting keyboard is assigned a Cartesian coordinate to simplify the calculation of the distance to keystrokes. The distance between the contacted point and the various candidate character locations in the auto-correcting keyboard, therefore, is calculated through simple Cartesian coordinate distance analysis. In another embodiment of the invention, the square of the simple Cartesian coordinate distance is used to both simplify calculation (because no square root need be calculated) and to apply a non-linear weighting to more distant contact points. In other embodiments, the distance calculation also utilizes other nonlinear functions such as natural logarithms or discrete steps, either exclusively or in an appropriately weighted combination with Cartesian coordinate distance analysis.

Also, in another preferred embodiment the distances in the x and y directions are weighted differently. Such modifications to the distance calculation can serve to simplify word selection, reduce processing requirements, or to accommodate systematic entry anomalies depending on the particular needs of a given system and its implementation. For example, in the case of a touch screen display panel on which a QWERTY keyboard arrangement is displayed with three rows of character keys, it is generally less likely that a significant error will be made in contacting the keyboard in the wrong row. In this case, vertical distance along the y-axis may be weighted more heavily than horizontal distance along the x-axis.

Additionally, the spacing between characters on the auto-correcting keyboard may be non-uniform, depending on how frequently any given character is used in a representative corpus of the language, or on its location relative to the center or the edge of the keyboard. Alternatively, when sufficient computational resources are available, one or more characters may be assigned a plurality of corresponding coordinate locations to be used as reference points in calculating the distance of the key from the coordinate location of a point at which the keyboard was contacted, wherein that distance is calculated as the distance from the contacted point to the closest such assigned reference coordinate. This will tend to decrease the calculated distances to points at which the display is contacted in a non-linear fashion, and consequently increase the size of the region surrounding the character in which there is a high likelihood that a sequence of contacts that includes a contact point in the region will match a word with the character in the corresponding position.

Also, the coordinates of the characters may be assigned to locations not shared by keyboard keys or directly detectable by sensors. This allows the system to be implemented using less costly touch screens or keyboards having a lower resolution in detecting points of contact. It also allows the keyboard to be reconfigured according to the user's wishes but still utilizing the same physical keyboard touch screen or sensor array. For example, the common three rows of characters in the QWERTY layout may be served with 1, 2, 3 or more rows of sensors to reduce the keyboard's mechanical complexity or to allow dynamic reassignment of novel keyboard arrays. An example would be changing from 3 rows of 9 characters to 4 rows of 7 characters. The assigned coordinate location for a given character key may thus lie between the nearest two or mor