Method, apparatus, and computer readable medium for performing semantic analysis and generating a semantic structure having linked frames

• US 6,243,670 B1
• Filed: 08/31/1999
• Issued: 06/05/2001
• Est. Priority Date: 09/02/1998
• Status: Expired due to Fees

• Current Assignee: Nippon Telegraph and Telephone Corporation
• Original Assignee: Nippon Telegraph and Telephone Corporation
• Inventors: Bessho, Katsuji, Iwase, Shigehito
• Primary Examiner(s): Thomas, Joseph
• Application Number:
  US09/386,996
• Time in Patent Office: 644 Days
• Field of Search: 704/9, 704/1, 704/10, 707/2, 707/3, 707/4, 707/5, 707/6, 707/7, 707/104, 707/531, 707/532, 707/533
• US Class Current: 704/9
• CPC Class Codes: G06F 40/30 Semantic analysis
• CPC Class Codes: Y10S 707/99934 Query formulation, input preparation, or translation

Abstract

A method for performing a semantic analysis process on a computer system including a storage unit and an interface includes the steps of: receiving a syntactic tree generated from a natural language sentence text; determining whether an analysis object, which is one of nodes of the syntactic tree, is a verb phrase class which has a verb as a head or a non-verb phrase class which has mainly a noun as the head on the basis of subdivided type information of a phrase of the node with reference to first data stored in the storage unit; analyzing a relation between a verb in the analysis object and a deep case of the verb when the analysis object is the verb phrase class; analyzing a modificative relation in the analysis object when the analysis object is the non-verb phrase class; generating a semantic structure of the natural language sentence text wherein the semantic structure comprises semantic frames corresponding to nodes of the syntactic tree, at least two semantic frames of the semantic frames being linked by a head relation or a deep case relation or a modificative relation, and storing the semantic structure in the storage unit or displaying the semantic structure on a display which is connectable to the computer system via the interface.

Claims

1. A method for performing a semantic analysis process on a computer system including a storage unit and an interface, said method comprising the steps of:

receiving a syntactic tree generated from a natural language sentence text;

determining whether an, analysis object, which is one of nodes of said syntactic tree, is a verb phrase class which has a verb as a head or a non-verb phrase class which has mainly a noun as the head on the basis of subdivided type information of a phrase of said node with reference to first data stored in said storage unit;

analyzing a relation between a verb in said analysis object and a deep case of said verb when said analysis object is said verb phrase class;

analyzing a modificative relation in said analysis object when said analysis object is said non-verb phrase class;

generating a semantic structure of said natural language sentence text wherein said semantic structure comprises semantic frames corresponding to nodes of said syntactic tree, at least two semantic frames of said semantic frames being linked by a head relation or a deep case relation or a modificative relation; and

storing said semantic structure in said storage unit or displaying said semantic structure on a display which is connectable to said computer system via said interface;

wherein said step of analyzing a relation between a verb and a deep case of said verb comprises the steps of;

(a) setting a head verb frame corresponding to a head verb node which is the head of said analysis object, and linking an analysis object frame corresponding to said analysis object and said head verb frame by said head relation;

(b) determining the voice of said analysis object with reference to voice information accompanying a node including said analysis object;

(c) determining a deep case to be extracted from deep cases included in verb semantic information accompanying said head verb node; and

(d) obtaining a syntactic tree node corresponding to said deep case determined in said step (c), setting a deep case frame corresponding to said syntactic tree node, and linking said head verb frame and said deep case frame by said deep case relation.

2. The method as claimed in claim 1, further comprising the steps of;

determining whether said analysis object is a part of speech, and

completing said semantic analysis process if said analysis object is said part of speech.

3. A method for performing a semantic analysis process on a computer system including a storage unit and an interface, said method comprising the steps of:

receiving a syntactic tree generated from a natural language sentence text;

determining whether an, analysis object, which is one of nodes of said syntactic tree, is a verb phrase class which has a verb as a head or a non-verb phrase class which has mainly a noun as the head on the basis of subdivided type information of a phrase of said node with reference to first data stored in said storage unit;

analyzing a relation between a verb in said analysis object and a deep case of said verb when said analysis object is said verb phrase class;

analyzing a modificative relation in said analysis object when said analysis object is said non-verb phrase class;

generating a semantic structure of said natural language sentence text wherein said semantic structure comprises semantic frames corresponding to nodes of said syntactic tree, at least two semantic frames of said semantic frames being linked by a head relation or a deep case relation or a modificative relation; and

storing said semantic structure in said storage unit or displaying said semantic structure on a display which is connectable to said computer system via said interface;

wherein said step of analyzing a relation between a verb and a deep case of said verb comprises the steps of;

(a) obtaining a head verb node which is the head of said analysis object with reference to second data stored in said storage unit, setting a head verb frame corresponding to said head verb node, and linking an analysis object frame corresponding to said analysis object and said head verb frame by said head relation;

(b) determining the voice of said analysis object with reference to voice information accompanying a node including said analysis object;

(c) determining a deep case to be extracted from deep cases included in verb semantic information accompanying said head verb node;

(d) obtaining a syntactic tree node corresponding to said deep case determined in said step (c), setting a deep case frame corresponding to said syntactic tree node, and linking said head verb frame and said deep case frame by said deep case relation;

(e) performing said semantic analysis process for said deep case frame if said deep case frame is set in said step (d), and

(f) performing said step (c) when said step (e) completes, and completing said semantic analysis process if there is no deep case to be extracted in said deep cases included in verb semantic information when performing said step (c).

4. The method as claimed in claim 3, wherein said step (d) comprises the steps of:

obtaining a surface case corresponding to said deep case determined in said step (c) with reference to said voice determined in said step (b) and verb semantic information accompanying said head verb node;

obtaining a syntactic tree node corresponding to said surface case with reference to said surface case and said second data stored in said storage unit;

comparing information with constraint condition knowledge of said deep case in said verb semantic information, said information including phrase type information, the subdivided type information and semantic information, said information accompanying said syntactic tree node, and

setting a deep case frame corresponding to said syntactic tree node and linking said head verb frame and said deep case frame by said deep case relation if said information is the same as said constraint condition knowledge.

5. The method as claimed in claim 4, further comprising the steps of obtaining moved surface case information and generating a deep case frame if said surface case or said syntactic tree node can not be obtained or if there is not said syntactic tree node accompanied with said information which is the same as said constraint condition knowledge.

6. A method for performing a semantic analysis process on a computer system including a storage unit and an interface, said method comprising the steps of:

receiving a syntactic tree generated from a natural language sentence text;

determining whether an, analysis object, which is one of nodes of said syntactic tree, is a verb phrase class which has a verb as a head or a non-verb phrase class which has mainly a noun as the head on the basis of subdivided type information of a phrase of said node with reference to first data stored in said storage unit;

analyzing a relation between a verb in said analysis object and a deep case of said verb when said analysis object is said verb phrase class;

analyzing a modificative relation in said analysis object when said analysis object is said non-verb phrase class;

generating a semantic structure of said natural language sentence text wherein said semantic structure comprises semantic frames corresponding to nodes of said syntactic tree, at least two semantic frames of said semantic frames being linked by a head relation or a deep case relation or a modificative relation; and

storing said semantic structure in said storage unit or displaying said semantic structure on a display which is connectable to said computer system via said interface;

wherein said step of analyzing a relation between a verb and a deep case of said verb comprising the steps of;

(a) obtaining a head verb node which is the head of said analysis object with reference to second data stored in said storage unit, setting a head verb frame corresponding to said head verb node, and linking an analysis object frame corresponding to said analysis object and said head verb frame by said head relation;

(b) determining a head verb frame to be processed from said head verb frames set in said step (a);

(c) determining the voice of said analysis object with reference to voice information accompanying a node including said analysis object;

(d) determining a deep case to be extracted from deep cases included in verb semantic information accompanying said head verb node;

(e) obtaining a syntactic tree node corresponding to said deep case determined in said step (d), setting a deep case frame corresponding to said syntactic tree node, and linking said head verb frame and said deep case frame by said deep case relation;

(f) determining a deep case frame to be processed from said deep case frames set in said step (e);

(g) performing said semantic analysis process for said deep case frame determined in said step (f), and

(h) performing said step (f) when said step (g) completes, performing said step (d) if there is no deep case frame to be processed in said deep case frames when performing said step (f), performing said step (b) if there is no deep case to be extracted in said deep cases included in verb semantic information when performing said step (d), and completing said semantic analysis process if there is no head verb frame to be processed in said head verb frames when performing said step (b).

7. A method for performing a semantic analysis process on a computer system including a storage unit and an interface, said method comprising the steps of:

receiving a syntactic tree generated from a natural language sentence text;

determining whether an, analysis object, which is one of nodes of said syntactic tree, is a verb phrase class which has a verb as a head or a non-verb phrase class which has mainly a noun as the head on the basis of subdivided type information of a phrase of said node with reference to first data stored in said storage unit;

analyzing a relation between a verb in said analysis object and a deep case of said verb when said analysis object is said verb phrase class;

analyzing a modificative relation in said analysis object when said analysis object is said non-verb phrase class;

generating a semantic structure of said natural language sentence text wherein said semantic structure comprises semantic frames corresponding to nodes of said syntactic tree, at least two semantic frames of said semantic frames being linked by a head relation or a deep case relation or a modificative relation; and

storing said semantic structure in said storage unit or displaying said semantic structure on a display which is connectable to said computer system via said interface;

wherein said step of analyzing a modificative relation comprises the steps of;

(a) obtaining a head node which is the head of said analysis object with reference to second data stored in said storage unit, setting a head frame corresponding to said head node, and linking an analysis object frame corresponding to said analysis object and said head frame by said head relation;

(b) performing said semantic analysis process for said head frame;

(c) obtaining a modificative phrase node which modifies said head node with reference to said second data stored in said storage unit, setting a modificative phrase frame corresponding to said modificative phrase node, and linking said head frame and said modificative phrase frame by said modificative relation;

(d) determining whether said modificative phrase frame is set when performing said step (c);

(e) performing said semantic analysis process for said modificative phrase frame if said modificative phrase frame is determined to be set in said step (d), and

(f) performing said step (c) when said step (e) completes, completing said semantic analysis process if said modificative phrase frame is not determined to be set in said step (d).

8. A method for performing a semantic analysis process on a computer system including a storage unit and an interface, said method comprising the steps of:

receiving a syntactic tree generated from a natural language sentence text;

determining whether an, analysis object, which is one of nodes of said syntactic tree, is a verb phrase class which has a verb as a head or a non-verb phrase class which has mainly a noun as the head on the basis of subdivided type information of a phrase of said node with reference to first data stored in said storage unit;

analyzing a relation between a verb in said analysis object and a deep case of said verb when said analysis object is said verb phrase class;

analyzing a modificative relation in said analysis object when said analysis object is said non-verb phrase class;

generating a semantic structure of said natural language sentence text wherein said semantic structure comprises semantic frames corresponding to nodes of said syntactic tree, at least two semantic frames of said semantic frames being linked by a head relation or a deep case relation or a modificative relation; and

storing said semantic structure in said storage unit or displaying said semantic structure on a display which is connectable to said computer system via said interface;

wherein said step of analyzing a modificative relation comprises the steps of;

(a) obtaining a head node which is the head of said analysis object with reference to second data stored in said storage unit, setting a head frame corresponding to said head node, and linking an analysis object frame corresponding to said analysis object and said head frame by said head relation;

(b) determining a head frame to be processed from said head frames set in said step (a);

(c) performing said semantic analysis process for said head frame determined in said step (b);

(d) obtaining a modificative phrase node which modifies said head node with reference to said second data stored in said storage unit, setting a modificative phrase frame corresponding to said modificative phrase node, and linking said head frame and said modificative phrase frame by said modificative relation;

(e) determining a modificative phrase frame to be processed from said modificative phrase frames set in said step (d);

(f) performing said semantic analysis process for said modificative phrase frame determined in said step (e), and

(g) performing said step (e) when said step (f) completes, performing said step (b) if there is no modificative phrase frame to be processed in said modificative phrase frames when performing said step (e), and completing said semantic analysis process if there is no head frame to be processed in said head frames when performing said step (b).

9. A method for searching information which uses a method for performing a semantic analysis process on a computer system including a storage unit and an interface, said method including the steps of:

receiving a syntactic tree generated from a natural language sentence text;

determining whether an, analysis object, which is one of nodes of said syntactic tree, is a verb phrase class which has a verb as a head or a non-verb phrase class which has mainly a noun as the head on the basis of subdivided type information of a phrase of said node with reference to first data stored in said storage unit;

analyzing a relation between a verb in said analysis object and a deep case of said verb when said analysis object is said verb phrase class;

analyzing a modificative relation in said analysis object when said analysis object is said non-verb phrase class;

generating a semantic structure of said natural language sentence text wherein said semantic structure comprises semantic frames corresponding to nodes of said syntactic tree, at least two semantic frames of said semantic frames being linked by a head relation or a deep case relation or a modificative relation; and

storing said semantic structure in said storage unit or displaying said semantic structure on a display which is connectable to said computer system via said interface, said method for searching information comprising the steps of;

receiving a natural language sentence text via said interface;

performing a morphological analysis process and a syntax analysis process of said natural language sentence text and generating a syntactic tree of said natural language sentence text;

performing said semantic analysis process for said syntactic tree and generating a semantic structure of said natural language sentence text;

extracting a keyword representing an intention of a user of said computer system from said semantic structure;

obtaining a category name and address information corresponding to said natural language sentence text from said keyword with reference to at least a knowledge database stored in said storage unit;

obtaining information to be searched with said category name and said address information with reference to an information database stored in said storage unit, said information database including said information which is classified by said category name and said address information, and

sending obtained information via said interface to another computer system or displaying said information on a display which is connectable to said computer system.

10. An apparatus for performing a semantic analysis process, said apparatus including a storage unit and an interface, said apparatus comprising:

means for receiving a syntactic tree generated from a natural language sentence text;

first means for determining whether an analysis object, which is one of nodes of said syntactic tree, is a verb phrase class which has a verb as a head or a non-verb phrase class which has mainly a noun as the head on the basis of subdivided type information of a phrase of said node with reference to first data stored in said storage unit;

second means for analyzing a relation between a verb in said analysis object and a deep case of said verb when said analysis object is said verb phrase class;

third means for analyzing a modificative relation in said analysis object when said analysis object is said non-verb phrase class;

means for generating a semantic structure of said natural language sentence text wherein said semantic structure comprises semantic frames corresponding to nodes of said syntactic tree, at least two semantic frames of said semantic frames being linked by a head relation or a deep case relation or a modificative relation; and

wherein said semantic structure is stored in said storage unit or displayed on a display which is connectable to said apparatus via said interface;

wherein said second means for analyzing a relation between a verb and a deep case of said verb comprises;

fourth means for setting a head verb frame corresponding to a head verb node which is the head of said analysis object, and linking an analysis object frame corresponding to said analysis object and said head verb frame by said head relation;

fifth means for determining the voice of said analysis object with reference to voice information accompanying a node including said analysis object;

sixth means for determining a deep case to be extracted from deep cases included in verb semantic information accompanying said head verb node; and

seventh means for obtaining a syntactic tree node corresponding to said deep case determined in said sixth means, setting a deep case frame corresponding to said syntactic tree node, and linking said head verb frame and said deep case frame by said deep case relation.

11. The apparatus as claimed in claim 10, further comprising;

means for determining whether said analysis object is a part of speech, and

means for completing said semantic analysis process if said analysis object is said part of speech.

12. An apparatus for performing a semantic analysis process, said apparatus including a storage unit and an interface, said apparatus comprising:

means for receiving a syntactic tree generated from a natural language sentence text;

first means for determining whether an analysis object, which is one of nodes of said syntactic tree, is a verb phrase class which has a verb as a head or a non-verb phrase class which has mainly a noun as the head on the basis of subdivided type information of a phrase of said node with reference to first data stored in said storage unit;

second means for analyzing a relation between a verb in said analysis object and a deep case of said verb when said analysis object is said verb phrase class;

third means for analyzing a modificative relation in said analysis object when said analysis object is said non-verb phrase class;

means for generating a semantic structure of said natural language sentence text wherein said semantic structure comprises semantic frames corresponding to nodes of said syntactic tree, at least two semantic frames of said semantic frames being linked by a head relation or a deep case relation or a modificative relation; and

wherein said semantic structure is stored in said storage unit or displayed on a display which is connectable to said apparatus via said interface;

wherein said second means for analyzing a relation between a verb and a deep case of said verb comprises;

fourth means for obtaining a head verb node which is the head of said analysis object with reference to second data stored in said storage unit, setting a head verb frame corresponding to said head verb node, and linking an analysis object frame corresponding to said analysis object and said head verb frame by said head relation;

fifth means for determining the voice of said analysis object with reference to voice information accompanying a node including said analysis object;

sixth means for determining a deep case to be extracted from deep cases included in verb semantic information accompanying said head verb node;

seventh means for obtaining a syntactic tree node corresponding to said deep case determined in said sixth means, setting a deep case frame corresponding to said syntactic tree node, and linking said head verb frame and said deep case frame by said deep case relation;

eighth means for performing said semantic analysis process for said deep case frame if said deep case frame is set in said seventh means, and

ninth means for performing the process of said sixth means when the process of said eighth means completes, and completing said semantic analysis process if there is no deep case to be extracted in said deep cases included in verb semantic information in said sixth means.

13. The apparatus as claimed in claim 12, wherein said seventh means comprises:

means for obtaining a surface case corresponding to said deep case determined in said sixth means with reference to said voice determined in said fifth means and verb semantic information accompanying said head verb node;

means for obtaining a syntactic tree node corresponding to said surface case with reference to said surface case and said second data stored in said storage unit;

means for comparing information with constraint condition knowledge of said deep case in said verb semantic information, said information including phrase type information, the subdivided type information and semantic information, said information accompanying said syntactic tree node, and

means for setting a deep case frame corresponding to said syntactic tree node and linking said head verb frame and said deep case frame by said deep case relation if said information is the same as said constraint condition knowledge.

14. The apparatus as claimed in claim 13, further comprising means for obtaining moved surface case information and generating a deep case frame if said surface case or said syntactic tree node can not be obtained or if there is not said syntactic tree node accompanied with said information which is the same as said constraint condition knowledge.

15. An apparatus for performing a semantic analysis process, said apparatus including a storage unit and an interface, said apparatus comprising:

means for receiving a syntactic tree generated from a natural language sentence text;

first means for determining whether an analysis object, which is one of nodes of said syntactic tree, is a verb phrase class which has a verb as a head or a non-verb phrase class which has mainly a noun as the head on the basis of subdivided type information of a phrase of said node with reference to first data stored in said storage unit;

second means for analyzing a relation between a verb in said analysis object and a deep case of said verb when said analysis object is said verb phrase class;

third means for analyzing a modificative relation in said analysis object when said analysis object is said non-verb phrase class;

means for generating a semantic structure of said natural language sentence text wherein said semantic structure comprises semantic frames corresponding to nodes of said syntactic tree, at least two semantic frames of said semantic frames being linked by a head relation or a deep case relation or a modificative relation; and

wherein said semantic structure is stored in said storage unit or displayed on a display which is connectable to said apparatus via said interface;

wherein said second means of analyzing a relation between a verb and a deep case of said verb comprising the steps of;

fourth means for obtaining a head verb node which is the head of said analysis object with reference to second data stored in said storage unit, setting a head verb frame corresponding to said head verb node, and linking an analysis object frame corresponding to said analysis object and said head verb frame by said head relation;

fifth means for determining a head verb frame to be processed from said head verb frames set in said fourth means;

sixth means for determining the voice of said analysis object with reference to voice information accompanying a node including said analysis object;

seventh means for determining a deep case to be extracted from deep cases included in verb semantic information accompanying said head verb node;

eighth means for obtaining a syntactic tree node corresponding to said deep case determined in said seventh means, setting a deep case frame corresponding to said syntactic tree node, and linking said head verb frame and said deep case frame by said deep case relation;

ninth means for determining a deep case frame to be processed from said deep case frames set in said eighth means;

tenth means for performing said semantic analysis process for said deep case frame determined in said ninth means, and

eleventh means for performing the process of said ninth means when the process of said tenth means completes, performing the process of said seventh means if there is no deep case frame to be processed in said deep case frames in said ninth means, performing the process of said fifth means if there is no deep case to be extracted in said deep cases included in verb semantic information in said seventh means, and completing said semantic analysis process if there is no head verb frame to be processed in said head verb frames in said fifth means.

16. An apparatus for performing a semantic analysis process, said apparatus including a storage unit and an interface, said apparatus comprising:

means for receiving a syntactic tree generated from a natural language sentence text;

first means for determining whether an analysis object, which is one of nodes of said syntactic tree, is a verb phrase class which has a verb as a head or a non-verb phrase class which has mainly a noun as the head on the basis of subdivided type information of a phrase of said node with reference to first data stored in said storage unit;

second means for analyzing a relation between a verb in said analysis object and a deep case of said verb when said analysis object is said verb phrase class;

third means for analyzing a modificative relation in said analysis object when said analysis object is said non-verb phrase class;

means for generating a semantic structure of said natural language sentence text wherein said semantic structure comprises semantic frames corresponding to nodes of said syntactic tree, at least two semantic frames of said semantic frames being linked by a head relation or a deep case relation or a modificative relation; and

wherein said semantic structure is stored in said storage unit or displayed on a display which is connectable to said apparatus via said interface;

wherein said third means for analyzing a modificative relation comprises;

fourth means for obtaining a head node which is the head of said analysis object with reference to second data stored in said storage unit, setting a head frame corresponding to said head node, and linking an analysis object frame corresponding to said analysis object and said head frame by said head relation;

fifth means for performing said semantic analysis process for said head frame;

sixth means for obtaining a modificative phrase node which modifies said head node with reference to said second data stored in said storage unit, setting a modificative phrase frame corresponding to said modificative phrase node, and linking said head frame and said modificative phrase frame by said modificative relation;

seventh means for determining whether said modificative phrase frame is set when performing the process of said sixth means;

eighth means for performing said semantic analysis process for said modificative phrase frame if said modificative phrase frame is determined to be set in said seventh means, and

ninth means for performing the process of said sixth means when the process of said eighth means completes, completing said semantic analysis process if said modificative phrase frame is not determined to be set in said seventh means.

17. An apparatus for performing a semantic analysis process, said apparatus including a storage unit and an interface, said apparatus comprising:

means for receiving a syntactic tree generated from a natural language sentence text;

first means for determining whether an analysis object, which is one of nodes of said syntactic tree, is a verb phrase class which has a verb as a head or a non-verb phrase class which has mainly a noun as the head on the basis of subdivided type information of a phrase of said node with reference to first data stored in said storage unit;

second means for analyzing a relation between a verb in said analysis object and a deep case of said verb when said analysis object is said verb phrase class;

third means for analyzing a modificative relation in said analysis object when said analysis object is said non-verb phrase class;

means for generating a semantic structure of said natural language sentence text wherein said semantic structure comprises semantic frames corresponding to nodes of said syntactic tree, at least two semantic frames of said semantic frames being linked by a head relation or a deep case relation or a modificative relation; and

wherein said semantic structure is stored in said storage unit or displayed on a display which is connectable to said apparatus via said interface;

wherein said third means for analyzing a modificative relation comprises;

fourth means for obtaining a head node which is the head of said analysis object with reference to second data stored in said storage unit, setting a head frame corresponding to said head node, and linking an analysis object frame corresponding to said analysis object and said head frame by said head relation;

fifth means for determining a head frame to be processed from said head frames set in said fourth means;

sixth means for performing said semantic analysis process for said head frame determined in said fifth means;

seventh means for obtaining a modificative phrase node which modifies said head node with reference to said second data stored in said storage unit, setting a modificative phrase frame corresponding to said modificative phrase node, and linking said head frame and said modificative phrase frame by said modificative relation;

eighth means for determining a modificative phrase frame to be processed from said modificative phrase frames set in said seventh means;

ninth means for performing said semantic analysis process for said modificative phrase frame determined in said eighth means, and

tenth means for performing the process of said eighth means when the process of said ninth means completes, performing the process of said fifth means if there is no modificative phrase frame to be processed in said modificative phrase frames when performing the process of said eighth means, and completing said semantic analysis process if there is no head frame to be processed in said head frames when performing the process of said fifth means.

18. An apparatus for searching information which uses an apparatus for performing a semantic analysis process, said apparatus including a storage unit and an interface, said apparatus including:

means for receiving a syntactic tree generated from a natural language sentence text;

first means for determining whether an analysis object, which is one of nodes of said syntactic tree, is a verb phrase class which has a verb as a head or a non-verb phrase class which has mainly a noun as the head on the basis of subdivided type information of a phrase of said node with reference to first data stored in said storage unit;

second means for analyzing a relation between a verb in said analysis object and a deep case of said verb when said analysis object is said verb phrase class;

third means for analyzing a modificative relation in said analysis object when said analysis object is said non-verb phrase class;

means for generating a semantic structure of said natural language sentence text wherein said semantic structure comprises semantic frames corresponding to nodes of said syntactic tree, at least two semantic frames of said semantic frames being linked by a head relation or a deep case relation or a modificative relation; and

wherein said semantic structure is stored in said storage unit or displayed on a display which is connectable to said apparatus via said interface, said apparatus for searching information comprising;

means for receiving a natural language sentence text via said interface,

means for performing a morphological analysis process and a syntax analysis process for said natural language sentence text and generating a syntactic tree of said natural language sentence text;

means for performing said semantic analysis process for said syntactic tree and generating a semantic structure of said natural language sentence text;

means for extracting a keyword representing an intention of a user of said apparatus from said semantic structure;

means for obtaining a category name and address information corresponding to said natural language sentence text by using said keyword with reference to at least one knowledge database stored in said storage unit;

means for obtaining information to be searched by using said category name and said address information with reference to an information database stored in said storage unit, said information database including said information which is classified by said category name and said address information, and

means for sending obtained information via said interface to another computer system or displaying said information on said display which is connectable to said apparatus.

19. A computer readable medium storing program code for causing a computer system which includes a storage unit and an interface to perform a semantic analysis process, said computer readable medium comprising:

program code means for receiving a syntactic tree generated from a natural language sentence text;

first program code means for determining whether an analysis object, which is one of nodes of said syntactic tree, is a verb phrase class which has a verb as a head or a non-verb phrase class which has mainly a noun as the head on the basis of subdivided type information of a phrase of said node with reference to first data stored in said storage unit;

second program code means for analyzing a relation between a verb in said analysis object and a deep case of said verb when said analysis object is said verb phrase class;

third program code means for analyzing a modificative relation in said analysis object when said analysis object is said non-verb phrase class;

program code means for generating a semantic structure of said natural language sentence text wherein said semantic structure comprises semantic frames corresponding to nodes of said syntactic tree, at least two semantic frames of said semantic frames being linked by a head relation or a deep case relation or a modificative relation; and

program code means for storing said semantic structure in said storage unit or displaying said semantic structure on a display which is connectable to said computer system via said interface;

wherein said second program code means for analyzing a relation between a verb and a deep case of said verb comprises;

fourth program code means for setting a head verb frame corresponding to a head verb node which is the head of said analysis object, and linking an analysis object frame corresponding to said analysis object and said head verb frame be said head relation;

fifth program code means for determining the voice of said analysis object with reference to voice information accompanying a node including said analysis object;

sixth program code means for determining a deep case to be extracted from deep cases included in verb semantic information accompanying said head verb node; and

seventh program code means for obtaining a syntactic tree node corresponding to said deep case determined in said sixth program code means, setting a deep case frame corresponding to said syntactic tree node, and linking said head verb frame and said deep case frame by said deep case relation.

20. The computer readable medium as claimed in claim 19, further comprising;

program code means for determining whether said analysis object is a part of speech, and

program code means for completing said semantic analysis process if said analysis object is said part of speech.

21. A computer readable medium storing program code for causing a computer system which includes a storage unit and an interface to perform a semantic analysis process, said computer readable medium comprising:

program code means for receiving a syntactic tree generated from a natural language sentence text;

first program code means for determining whether an analysis object, which is one of nodes of said syntactic tree, is a verb phrase class which has a verb as a head or a non-verb phrase class which has mainly a noun as the head on the basis of subdivided type information of a phrase of said node with reference to first data stored in said storage unit;

second program code means for analyzing a relation between a verb in said analysis object and a deep case of said verb when said analysis object is said verb phrase class;

third program code means for analyzing a modificative relation in said analysis object when said analysis object is said non-verb phrase class;

program code means for generating a semantic structure of said natural language sentence text wherein said semantic structure comprises semantic frames corresponding to nodes of said syntactic tree, at least two semantic frames of said semantic frames being linked by a head relation or a deep case relation or a modificative relation; and

program code means for storing said semantic structure in said storage unit or displaying said semantic structure on a display which is connectable to said computer system via said interface;

wherein said second program code means for analyzing a relation between a verb and a deep case of said verb comprises;

fourth program code means for obtaining a head verb node which is the head of said analysis object with reference to second data stored in said storage unit, setting a head verb frame corresponding to said head verb node, and linking an analysis object frame corresponding to said analysis object and said head verb frame by said head relation;

fifth program code means for determining the voice of said analysis object with reference to voice information accompanying a node including said analysis object;

sixth program code means for determining a deep case to be extracted from deep cases included in verb semantic information accompanying said head verb node;

seventh program code means for obtaining a syntactic tree node corresponding to said deep case determined in said sixth program code means, setting a deep case frame corresponding to said syntactic tree node, and linking said head verb frame and said deep case frame by said deep case relation;

eighth program code means for performing said semantic analysis process for said deep case frame if said deep case frame is set in said seventh program code means, and

ninth program code means for performing the process of said sixth program code means when the process of said eighth program code means completes, and completing said semantic analysis process if there is no deep case to be extracted in said deep cases included in verb semantic information in said sixth program code means.

22. The computer readable medium as claimed in claim 21, wherein said seventh program code means comprises:

program code means for obtaining a surface case corresponding to said deep case determined in said sixth program code means with reference to said voice determined in said fifth program code means and verb semantic information accompanying said head verb node;

program code means for obtaining a syntactic tree node corresponding to said surface case with reference to said surface case and said second data stored in said storage unit;

program code means for comparing information with constraint condition knowledge of said deep case in said verb semantic information, said information including phrase type information, the subdivided type information and semantic information, said information accompanying said syntactic tree node, and

program code means for setting a deep case frame corresponding to said syntactic tree node and linking said head verb frame and said deep case frame by said deep case relation if said information is the same as said constraint condition knowledge.

23. The computer readable medium as claimed in claim 22, further comprising program code means for obtaining moved surface case information and generating a deep case frame if said surface case or said syntactic tree node can not be obtained or if there is not said syntactic tree node accompanied with said information which is the same as said constraint condition knowledge.

24. A computer readable medium storing program code for causing a computer system which includes a storage unit and an interface to perform a semantic analysis process, said computer readable medium comprising:

program code means for receiving a syntactic tree generated from a natural language sentence text;

first program code means for determining whether an analysis object, which is one of nodes of said syntactic tree, is a verb phrase class which has a verb as a head or a non-verb phrase class which has mainly a noun as the head on the basis of subdivided type information of a phrase of said node with reference to first data stored in said storage unit;

second program code means for analyzing a relation between a verb in said analysis object and a deep case of said verb when said analysis object is said verb phrase class;

third program code means for analyzing a modificative relation in said analysis object when said analysis object is said non-verb phrase class;

program code means for generating a semantic structure of said natural language sentence text wherein said semantic structure comprises semantic frames corresponding to nodes of said syntactic tree, at least two semantic frames of said semantic frames being linked by a head relation or a deep case relation or a modificative relation; and

program code means for storing said semantic structure in said storage unit or displaying said semantic structure on a display which is connectable to said computer system via said interface;

wherein said second program code means for analyzing a relation between a verb and a deep case of said verb comprises;

fourth program code means for obtaining a head verb node which is the head of said analysis object with reference to second data stored in said storage unit, setting a head verb frame corresponding to said head verb node, and linking an analysis object frame corresponding to said analysis object and said head verb frame by said head relation;

fifth program code means for determining a head verb frame to be processed from said head verb frames set in said fourth program code means;

sixth program code means for determining the voice of said analysis object with reference to voice information accompanying a node including said analysis object;

seventh program code means for determining a deep case to be extracted from deep cases included in verb semantic information accompanying said head verb node;

eighth program code means for obtaining a syntactic tree node corresponding to said deep case determined in said seventh program code means, setting a deep case frame corresponding to said syntactic tree node, and linking said head verb frame and said deep case frame by said deep case relation;

ninth program code means for determining a deep case frame to be processed from said deep case frames set in said eighth program code means;

tenth program code means for performing said semantic analysis process for said deep case frame determined in said ninth program code means, and

eleventh program code means for performing the process of said ninth program code means when the process of said tenth program code means completes, performing the process of said seventh program code means if there is no deep case frame to be processed in said deep case frames in said ninth program code means, performing the process of said fifth program code means if there is no deep case to be extracted in said deep cases included in verb semantic information in said seventh program code means, and completing said semantic analysis process if there is no head verb frame to be processed in said head verb frames in said fifth program code means.

25. A computer readable medium storing program code for causing a computer system which includes a storage unit and an interface to perform a semantic analysis process, said computer readable medium comprising:

program code means for receiving a syntactic tree generated from a natural language sentence text;

first program code means for determining whether an analysis object, which is one of nodes of said syntactic tree, is a verb phrase class which has a verb as a head or a non-verb phrase class which has mainly a noun as the head on the basis of subdivided type information of a phrase of said node with reference to first data stored in said storage unit;

second program code means for analyzing a relation between a verb in said analysis object and a deep case of said verb when said analysis object is said verb phrase class;

third program code means for analyzing a modificative relation in said analysis object when said analysis object is said non-verb phrase class;

program code means for generating a semantic structure of said natural language sentence text wherein said semantic structure comprises semantic frames corresponding to nodes of said syntactic tree, at least two semantic frames of said semantic frames being linked by a head relation or a deep case relation or a modificative relation; and

program code means for storing said semantic structure in said storage unit or displaying said semantic structure on a display which is connectable to said computer system via said interface;

wherein said third program code means for analyzing a modificative relation comprises;

fourth program code means for obtaining a head node which is the head of said analysis object with reference to second data stored in said storage unit, setting a head frame corresponding to said head node, and linking an analysis object frame corresponding to said analysis object and said head frame by said head relation;

fifth program code means for performing said semantic analysis process for said head frame;

sixth program code means for obtaining a modificative phrase node which modifies said head node with reference to said second data stored in said storage unit, setting a modificative phrase frame corresponding to said modificative phrase node, and linking said head frame and said modificative phrase frame by said modificative relation;

seventh program code means for determining whether said modificative phrase frame is set when performing the process of said sixth program code means;

eighth program code means for performing said semantic analysis process for said modificative phrase frame if said modificative phrase frame is determined to be set in said seventh program code means, and

ninth program code means for performing the process of said sixth program code means when the process of said eighth program code means completes, completing said semantic analysis process if said modificative phrase frame is not determined to be set in said seventh program code means.

26. A computer readable medium storing program code for causing a computer system which includes a storage unit and an interface to perform a semantic analysis process, said computer readable medium comprising:

program code means for receiving a syntactic tree generated from a natural language sentence text;

first program code means for determining whether an analysis object, which is one of nodes of said syntactic tree, is a verb phrase class which has a verb as a head or a non-verb phrase class which has mainly a noun as the head on the basis of subdivided type information of a phrase of said node with reference to first data stored in said storage unit;

second program code means for analyzing a relation between a verb in said analysis object and a deep case of said verb when said analysis object is said verb phrase class;

third program code means for analyzing a modificative relation in said analysis object when said analysis object is said non-verb phrase class;

program code means for generating a semantic structure of said natural language sentence text wherein said semantic structure comprises semantic frames corresponding to nodes of said syntactic tree, at least two semantic frames of said semantic frames being linked by a head relation or a deep case relation or a modificative relation; and

program code means for storing said semantic structure in said storage unit or displaying said semantic structure on a display which is connectable to said computer system via said interface;

wherein said third program code means for analyzing a modificative relation comprises;

fourth program code means for obtaining a head node which is the head of said analysis object with reference to second data stored in said storage unit, setting a head frame corresponding to said head node, and linking an analysis object frame corresponding to said analysis object and said head frame by said head relation;

fifth program code means for determining a head frame to be processed from said head frames set in said fourth program code means;

sixth program code means for performing said semantic analysis process for said head frame determined in said fifth program code means;

seventh program code means for obtaining a modificative phrase node which modifies said head node with reference to said second data stored in said storage unit, setting a modificative phrase frame corresponding to said modificative phrase node, and linking said head frame and said modificative phrase frame by said modificative relation;

eighth program code means for determining a modificative phrase frame to be processed from said modificative phrase frames set in said seventh program code means;

ninth program code means for performing said semantic analysis process for said modificative phrase frame determined in said eighth program code means, and

tenth program code means for performing the process of said eighth program code means when the process of said ninth program code means completes, performing the process of said fifth program code means if there is no modificative phrase frame to be processed in said modificative phrase frames when performing the process of said eighth program code means, and completing said semantic analysis process if there is no head frame to be processed in said head frames when performing the process of said fifth program code means.

27. A computer readable medium which includes a computer readable medium storing program code for causing a computer system which includes a storage unit and an interface to perform a semantic analysis process, said computer readable medium including:

program code means for receiving a syntactic tree generated from a natural language sentence text;

first program code means for determining whether an analysis object, which is one of nodes of said syntactic tree, is a verb phrase class which has a verb as a head or a non-verb phrase class which has mainly a noun as the head on the basis of subdivided type information of a phrase of said node with reference to first data stored in said storage unit;

second program code means for analyzing a relation between a verb in said analysis object and a deep case of said verb when said analysis object is said verb phrase class;

third program code means for analyzing a modificative relation in said analysis object when said analysis object is said non-verb phrase class;

program code means for generating a semantic structure of said natural language sentence text wherein said semantic structure comprises semantic frames corresponding to nodes of said syntactic tree, at least two semantic frames of said semantic frames being linked by a head relation or a deep case relation or a modificative relation; and

program code means for storing said semantic structure in said storage unit or displaying said semantic structure on a display which is connectable to said computer system via said interface, said computer readable medium comprising;

program code means for receiving a natural language sentence text via said interface,

program code means for performing a morphological analysis process and a syntax analysis process for said natural language sentence text and generating a syntactic tree of said natural language sentence text;

program code means for performing said semantic analysis process for said syntactic tree and generating a semantic structure of said natural language sentence text;

program code means for extracting a keyword representing an intention of a user of said computer system from said semantic structure;

program code means for obtaining a category name and address information corresponding to said natural language sentence text by using said keyword with reference to at least one knowledge database stored in said storage unit;

program code means for obtaining information to be searched by using said category name and said address information with reference to an information database stored in said storage unit, said information database including said information which is classified by said category name and said address information, and

program code means for sending obtained information via said interface to another computer system or displaying said information on a display which is connectable to said computer system.