Apparatus and method for handwriting recognition

1. A method comprising:

receiving a handwritten input character string having an unrecognized character;

determining at least one character sub-string preceding the unrecognized character in the input character string;

providing, by means of handwriting recognition, one or more candidate characters for the unrecognized character;

identifying, amongst stored character strings, one or more character strings comprising an initial character sub-string identical to the determined character sub-string; and

selecting, based on the identified one or more character strings, one of the one or more candidate characters that is most likely to be a correct recognition of the unrecognized character,

wherein if a complete character string preceding the unrecognized character in the input character string is not identical to any stored character string or an initial sub-string of any stored character string, determining at least one character sub-string comprises:

identifying any initial character sub-string of the input character string preceding the unrecognized character, which is identical to one of the stored character strings or to an initial character sub-string of one or more of the stored character strings, and which together with a succeeding character is not identical to any one of the stored character strings or to an initial character sub-string of any one of the stored character strings; and

determining a character sub-string consisting of a terminal character sub-string of the input character string preceding the unrecognized character and succeeding any identified initial character sub-string;

else determining at least one character sub-string comprises:

determining a character sub-string consisting of said complete character string preceding the unrecognized character in the input character string.

2. The method of claim 1 , wherein the one of the one or more candidate characters is selected which has the highest probability to succeed the character sub-string.

3. The method of claim 1 , wherein the selecting is further based on a next character succeeding the unrecognized character.

4. The method of claim 1 , wherein determining at least one character sub-string further comprises comparing the character sub-string to stored character strings, the stored character strings being chosen from the following type of character strings: phrases, words, word stubs and frequently used character sequences.

5. The method of claim 1 , wherein the determining of a character sub-string comprises:

identifying space characters in the input character string; and

on basis of a substring directly succeeding a space character and directly preceding the unrecognized character, determining a character sub-string.

6. The method of claim 5 , wherein a character sub-string is determined consisting of the terminal character sub-string of the input character string preceding the unrecognized character and succeeding an identified last space character before the unrecognized character.

7. The method of claim 1 , further comprising:

for each character in sequence of the input character string preceding the unrecognized character:

providing, by means of handwriting recognition, one or more candidate characters for the unrecognized character; and

selecting, based on the characters preceding the unrecognized character in the input character string, one of the one or more candidate characters which is most likely to be a correct recognition of the unrecognized character.

8. The method of claim 1 wherein recognizing the character sub-string comprises:

identifying at least one word string in the at least one character sub-string.

9. The method of claim 8 wherein identifying the at least one word string in the at least one character sub-string comprises

beginning with a character preceding the unrecognized character, comparing the character, and then the character together with each subsequent character, in order, to stored character strings.

10. An apparatus comprising:

a processor;

memory including computer program code;

the memory and the computer program code configured to, with the processor, cause the apparatus to:

receive a handwritten input character string having an unrecognized character;

determine at least one character sub-string preceding the unrecognized character in the input character string;

provide, by means of handwriting recognition, one or more candidate characters for the unrecognized character;

identify, amongst stored character strings, one or more character strings comprising an initial character sub-string identical to the determined character sub-string; and

select, based on the identified one or more character strings, one of the one or more candidate characters that is most likely to be a correct recognition of the unrecognized character,

wherein if a complete character string preceding the unrecognized character in the input character string is not identical to any stored character string or an initial sub-string of any stored character string, the apparatus is caused to determine at least one character sub-string by:

identifying any initial character sub-string of the input character string preceding the unrecognized character, which is identical to one of the stored character strings or to an initial character sub-string of one or more of the stored character strings, and which together with a succeeding character is not identical to any one of the stored character strings or to an initial character sub-string of any one of the stored character strings; and

determining a character sub-string consisting of a terminal character sub-string of the input character string preceding the unrecognized character and succeeding any identified initial character sub-string;

else the apparatus is caused to determine at least one character sub-string by:

determining a character sub-string consisting of said complete character string preceding the unrecognized character in the input character string.

11. The apparatus of claim 10 , wherein processor is arranged to select the candidate character is which has the highest probability to succeed the character sub-string.

12. The apparatus of claim 10 , wherein the processor is arranged to select, based on a next character succeeding the initial character sub-string of each of the one or more candidate character strings, one of the one or more candidate characters which is most likely to be a correct recognition of the unrecognized character.

13. The apparatus of claim 10 , wherein the processor is further arranged to:

identify space characters in the input character string, and

determine a character sub-string consisting of the terminal character sub-string of the input character string preceding the unrecognized character and succeeding an identified last space character before the unrecognized character.

14. The apparatus of claim 10 , wherein the stored character strings are chosen from the following type of character strings: phrases, words, word stubs and frequently used character sequences.

15. The apparatus of claim 10 , wherein the apparatus is a mobile terminal.

16. A mobile terminal comprising:

an interface for retrieving handwritten input representing an input character string with an unrecognized character;

a memory for storing frequently occurring character strings; and

a processor configured to:

determine at least one character sub-string preceding the unrecognized character in the input character string;

identify, amongst the stored character strings, one or more character strings comprising an initial character sub-string identical to the determined character sub-string preceding the unrecognized character,

provide, by means of handwriting recognition, one or more candidate characters for the unrecognized character,

identifying one or more character strings that include at least a combination of the determined character sub-string preceding the unrecognized character and one of the one or more candidate characters; and

select, based on a next character succeeding the initial character sub-string of each of the one or more candidate character strings, one of the one or more candidate characters which is most likely to be a correct recognition of the unrecognized character,

wherein if a complete character string preceding the unrecognized character in the input character string is not identical to any stored character string or an initial sub-string of any stored character string, the processor is configured to determine at least one character sub-string by:

identifying any initial character sub-string of the input character string preceding the unrecognized character, which is identical to one of the stored character strings or to an initial character sub-string of one or more of the stored character strings, and which together with a succeeding character is not identical to any one of the stored character strings or to an initial character sub-string of any one of the stored character strings; and

determining a character sub-string consisting of a terminal character sub-string of the input character string preceding the unrecognized character and succeeding any identified initial character sub-string;

else the processor is configured to determine at least one character sub-string by:

determining a character sub-string consisting of said complete character string preceding the unrecognized character in the input character string.

17. The mobile terminal of claim 16 , wherein the processor is further arranged to:

identify space characters in the input character string, and to determine a character sub-string consisting of the terminal character sub-string of the input character string preceding the unrecognized character and succeeding an identified last space character before the unrecognized character.

18. The mobile terminal of claim 16 , wherein the processor is arranged to determine a character sub-string by:

identifying space characters in the input character string;

identifying any initial character sub-string of the input character string preceding the unrecognized character and succeeding an identified last space character before the unrecognized character, which is identical to one of the stored character strings or to an initial character sub-string of one or more of the stored character strings, and which together with a succeeding character is not identical to any one of the stored character strings or to an initial character sub-string of any one of the stored character strings; and

determining a character sub-string consisting of the terminal character sub-string of the input character string preceding the unrecognized character and succeeding any identified initial character sub-string.