Question sentence generating device and computer program

1. A question sentence generating device for use with a question-answering system, the question sentence generating device comprising:

an interface configured to receive a word or a word sequence as a source for generating a question sentence; and

a memory including a database comprised of a plurality of records for generating question sentences, wherein:

each of said plurality of records has a key word and is generated from an answer having an answer sentence pattern co-occurring with the key word;

a processor configured to:

using the received word as a key, search and retrieve from said question sentence generating database an answer sentence pattern;

generate a question sentence from the retrieved answer sentence pattern and said received word, comprising:

generating question candidates by (1) transforming the retrieved answer sentence pattern into a plurality of question patterns and (2) combining each of the plurality of question patterns with the received word;

scoring each of the question candidates, wherein the score indicates a fit of each question sentence candidate as being a question having as an answer the answer from which the answer sentence pattern is generated; and

selecting as the question sentence the question sentence candidate having a best score; and

output the generated question sentence.

2. The question sentence generating device according to claim 1 , wherein:

the memory additional includes a synonym dictionary configured to store synonymous relation or entailment relation of a word or an answer sentence pattern or both; and

the processor is further configured to:

generate a plurality of question sentences;

select distinct ones of said generated plurality of question sentences to generate a smaller number of question sentences by referring to said synonym dictionary; and

output the generated smaller number of question sentence.

3. The question sentence generating device according to claim 1 , wherein:

the memory additional includes a thesaurus configured to store classification information for classifying words or answer sentence patterns or both systematically in accordance with their meanings; and

the processor is further configured to:

generate a plurality of question sentences;

select distinct ones of said generated plurality of question sentences to a smaller number of question sentences by referring to said thesaurus; and

output the generated smaller number of question sentences.

4. The question sentence generating device according to claim 1 , wherein

said processor is configured to:

receive a plurality of words; and

search said question sentence generating database, using the received plurality of words, for an answer sentence pattern co-occurring with the received plurality of words.

5. The question sentence generating device according to claim 1 , wherein

said processor is further configured to:

search and retrieve said question sentence generating database for an answer sentence pattern using the received word as a key;

generate a question sentence and an answer sentence to the question sentence from the retrieved answer sentence pattern and said received word; and

output the generated question sentence and the generated answer sentence to the question sentence.

6. The question sentence generating device according to claim 1 , wherein

said question-answering system includes a factoid type question-answering sub-system responsive to a factoid type question sentence;

said factoid type question-answering sub-system is configured to generate an answer sentence candidate by searching an answer sentence generating database using a key consisting of a pattern of the question sentence and a word or a word sequence included in the question sentence; and

said answer sentence generating database and said question sentence generating database include common records generated from the same corpus.

7. The question sentence generating device according to claim 1 , wherein:

said question-answering system further includes a non-factoid type question-answering sub-system responsive to a non-factoid type question;

said non-factoid type question-answering sub-system is configured:

to extract a plurality of passages as answer sentence candidates from a corpus,

to calculate a score indicating fitness as an answer to said given question by using a pre-learned scoring means, and

to output an answer sentence candidate having the highest score as an answer to said given question;

the memory further includes a question sentence database configured to store a plurality of question sentences each generated from any of a set of passages prepared in advance and not explicitly distinguished as a question or an answer and having as an answer a passage as a source of said question sentence;

the processor is further configured to:

receive a second word or a second word sequence as a source of generating a question sentence;

generate and output a new question sentence from the received second word or second word sequence as the source of generating the question sentence or synonyms or entailments of these and from a question sentence stored in said question sentence database by referring to said question sentence database; and

collectively output the generated question sentence and the generated new question sentence.

8. The question sentence generating device according to claim 1 , wherein the scoring of each of the question candidates is performed using a machine learning algorithm.

9. A question sentence generating device for use with a question-answering system, wherein:

said question-answering system includes:

a non-factoid type question-answering sub-system responsive to a non-factoid type question, wherein the non-factoid type question-answering sub-system is configured to:

extract a plurality of passages as answer sentence candidates from a corpus,

calculate a score for each passage, said score indicating fitness as an answer to said given question; and

output an answer sentence candidate having the highest score as an answer to said given question;

said question sentence generating device comprising:

a memory including a question sentence database configured to store a plurality of question sentences each generated from any passage in said corpus and having as an answer a passage as a source of generating the question sentence;

an interface configured to receive a word or a word sequence; and

a processor configured to generate and output a new question sentence from the received word or word sequence as the source of generating the question sentence or synonyms or entailments of these and from a question sentence stored in said question sentence database by referring to said question sentence database.

10. A computer program stored on a non-transitory computer readable medium causing a computer to function as a question sentence generating device for use with a question-answering system, wherein said computer is connected to a question sentence generating database comprising a plurality of records for generating question sentences, each of said plurality of records having a key word and is generated from an answer having an answer sentence pattern co-occurring with the word, wherein, when executed by a processor, said computer program causes said processor to:

receive a word or a word sequence as a source for generating a question sentence; and

search and retrieve from said question sentence generating database an answer sentence pattern using a key consisting of the received word;

generate a question sentence from the retrieved answer sentence pattern and said received word, comprising:

generating question candidates by (1) transforming the retrieved answer sentence pattern into a plurality of question patterns and (2) combining each of the plurality of question patterns with the received word;

scoring each of the question candidates, wherein the score indicates a fit of each question sentence candidate as being a question having as an answer the answer from which the answer sentence pattern is generated; and

selecting as the question sentence the question sentence candidate having a best score; and; and

output the generated question sentence.

11. The computer program according to claim 10 , wherein the scoring of each of the question candidates is performed using a machine learning algorithm.