Document data processing method and apparatus for document retrieval

• US 5,469,354 A
• Filed: 02/28/1992
• Issued: 11/21/1995
• Est. Priority Date: 06/14/1989
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Tada, Katsumi, Minegishi, Naoki, Hatakeyama, Atsushi, Asakawa, Satoshi, Fujisawa, Hiromichi, Kato, Kanji, Kawaguchi, Hisamitsu
• Primary Examiner(s): Weinhardt, Robert A.
• Assistant Examiner(s): Poinvil, Frantzy
• Application Number:
  US07/843,162
• Time in Patent Office: 1,362 Days
• Field of Search: 364/419.19, 364/419.13, 364/419.07, 364/225.3, 395/600
• US Class Current: 1/1
• CPC Class Codes: G06F 16/313 Selection or weighting of terms for indexing
• CPC Class Codes: G06F 16/90339 by using parallel associative memories or content-addressable memories
• CPC Class Codes: G06F 16/90344 by using string matching techniques
• CPC Class Codes: G06F 16/93 Document management systems
• CPC Class Codes: G06F 18/00 Pattern recognition
• CPC Class Codes: G06V 30/10 Character recognition
• CPC Class Codes: G06V 30/262 using context analysis, e.g. lexical, syntactic or semantic context
• CPC Class Codes: Y10S 707/99933 Query processing, i.e. searching

Abstract

High-speed full document retrieval method and system capable of providing result of retrieval within practically acceptable short search time. Upon registration of documents in a document database, condensed texts are created by decomposing each of textual character strings of the documents to be registered into fragmental character strings in dependence on character species and by checking mutual inclusion relations existing among the fragmental character strings. A component character table is created in which characters occurring in each of the condensed texts are registered without duplication. The condensed texts and the component character table are registered in the data base together with the texts of the documents to be registered. Upon retrieval of a document containing a search term designated by a user, a component character table search is first executed to extract those documents which contain all species of characters constituting the search term by consulting the component character table, and subsequently a condensed text search is executed by consulting the condensed texts of the documents. Finally, a text body search is executed for extracting a document which satisfies query condition imposed on the search term by consulting the texts of the documents extracted through the component character table search and the condensed text search.

Claims

1. A document data processing method for retrieving a document containing at least a search term designated by an operator from a document database registering therein document information in terms of character code data while referring to textual content of said document, comprising steps of:

upon registration of text documents in said document database,

creating condensed texts by decomposing each of textual character strings of the documents to be registered into fragmental character strings on the basis of at least one of character species including katakana character, hiragana character, kanji character, alphabetic character, numeric character, and symbol character and checking mutual inclusion relations possibly existing among said fragmental character strings resulting from said decomposition, to thereby create the condensed texts each constituted by a set of the fragmental character strings in which any character string found to be included by other character string is eliminated;

creating a component character table in which characters occurring in each of said condensed texts are registered without duplication; and

registering in said document database said condensed texts together with said component character table in addition to the texts of the document to be registered; and

upon retrieval of the document containing the designated search term, executing first a component character table search for thereby extracting those documents which contain all species of characters constituting the search term designated by the operator by consulting said component character table;

executing subsequently a condensed text search by consulting the condensed texts of the documents extracted through said component character table search for extracting only the documents corresponding to the condensed texts which contain the fragmental character strings constituting the search term designated by the operator to thereby select the documents containing the designated search term; and

executing finally a text body search for extracting a document which satisfies query condition imposed on the search term by consulting the texts of the documents extracted through said component character table search and said condensed text search.

2. A document data processing method for document retrieval according to claim 1, wherein said component character table registers without duplication all the characters as used on a document basis.

3. A document data processing method for document retrieval according to claim 2, wherein said component character table is created by mapping the character codes to a number of entry codes of said table which is smaller than a number of the characters used actually by using a hash function.

4. A document data processing method for document retrieval. according to claim 1, wherein in association with said component character table search, a bit list in which one-bit information allocated to all usable characters is prepared for each of said documents and wherein bit positions for the characters used in the documents are set to "1s" respectively, while the bit positions for the characters not used in the documents are set to "0s", respectively;

said component character table search is executed by searching said a bit list having all the bit positions set to "1s" for all the characters constituting said search term.

5. A document data processing method for document retrieval according to claim 4, wherein by mapping the character codes to a number of entry codes which is smaller than the number of the characters actually used, said bit list is realized by a number of bits which is smaller than a number of the character types actually used.

6. A document data processing method for document retrieval according to claim 5, wherein in association with said component character table search, a bit list in which one-bit information allocated to all usable characters is prepared for each of said documents and wherein bit positions for the characters used in the documents are set to "1s" respectively, while the bit positions for the characters not used in the documents are set to "0s", respectively;

said component character table search is executed by searching said bit list having all the bit positions set to "1s" for all the characters constituting said search term.

7. A document data processing method for document retrieval according to claim 6, wherein by mapping the character codes to a number of entry codes which is smaller than the number of the characters actually used, said bit list is realized by a number of bits which is smaller than a number of the characters actually used.

8. A document data processing method for document retrieval according to claim 1, wherein said text body search is executed when said search term is constituted with a plurality of character species and when said query condition includes a positional condition of the search term in the next text.

9. A document data processing method for retrieving a document containing at least a search term designated by an operator from a document database registering therein document information in terms of character code data while referring to textual content of said document, comprising steps of:

upon registration of text documents in said document database,

creating condensed texts by decomposing each of textual character strings of the documents to be registered into fragmental character strings on the basis of at least one of character species including katakana character, hiragana character, kanji character, alphabetic character, numeric character, and symbol character and checking mutual inclusion relations possibly existing among said fragmental character strings resulting from said decomposition, to thereby create the condensed texts each constituted by a set of the fragmental character strings in which any character string found to be included by other character string is eliminated;

creating a component character table in which characters occurring in registered texts are registered without duplication; and

registering in said document database said condensed texts together with said component character table in addition to the texts of the document to be registered; and

upon retrieval of the document containing the designated search term, executing first a component character table search for thereby extracting those documents which contain all species of characters constituting the search term designated by the operator by consulting said component character table;

executing subsequently a condensed text search by consulting the condensed texts of the documents extracted through said component character table search for extracting only the documents corresponding to the condensed texts which contain the fragmental character strings constituting the search term designated by the operator to thereby select the documents containing the designated search term; and

executing finally a text body search for extracting a document which satisfies query condition imposed on the search term by consulting the texts of the documents extracted through said component character table search and said condensed text search.

10. A document data processing method for document retrieval according to claim 9, wherein said component character table registers without duplication all the characters as used on a document basis.

11. A document data processing method for document retrieval according to claim 10, wherein said component character table is created by mapping the character codes to a number of entry codes of said table which is smaller than a number of the characters used actually by using a hash function.

12. A document data processing method for document retrieval according to claim 9, wherein said text body search is executed when said search term is constituted with a plurality of character species and when said query condition includes a positional condition of the search term in the next text.

13. A document data processing method for retrieving a document containing all of plural search terms designated by an operator from a document database registering therein document information in terms of character code data while referring to textual content of said document, comprising steps of:

upon registration of text documents in said document database,

creating condensed texts by decomposing each of textual character strings of the documents to be registered into fragmental character strings on the basis of at least one of character species including katakana character, hiragana character, kanji character, alphabetic character, numeric character and symbol character and checking mutual inclusion relations possibly existing among said fragmental character strings resulting from said decomposition, to thereby create the condensed texts each constituted by a set of the fragmental character strings in which any character string found to be included by other character string is eliminated;

creating a component character table in which characters occurring in registered texts are registered without duplication; and

registering in said document database said condensed texts together with said component character table in addition to the texts of the document to be registered; and

upon retrieval of the document containing the designated search term, executing first a component character table search for thereby extracting those documents which contain all species of characters constituting each of said search terms designated by the operator by consulting said component character table;

executing subsequently a condensed text search by consulting the condensed texts of the documents extracted through said component character table search for extracting only the documents corresponding to the condensed texts which contain all the fragmental character strings constituting each of said search terms designated by the operator to thereby select the documents containing the designated search terms; and

executing finally a text body search for extracting a document which satisfies query condition imposed on said search terms such as positional relation thereof in the text by consulting the texts of the documents extracted through said component character table search and said condensed text search.

14. A document data processing method for retrieving a document containing any one of search terms designated by an operator from a document database registering therein document information in terms of character code data while referring to textual content of said document, comprising steps of:

upon registration of text documents in said document database,

creating condensed texts by decomposing each of textual character strings of the documents to be registered into fragmental character strings on the basis of at least one of character species including katakana character, hiragana character, kanji character, alphabetic character, numeric character and symbol character and checking mutual inclusion relations possibly existing among said fragmental character strings resulting from said decomposition, to thereby create the condensed texts each constituted by a set of the fragmental character strings in which any character string found to be included by other character string is eliminated;

creating a component character table in which characters occurring in registered texts are registered without duplication; and

registering in said document database said condensed texts together with said component character table in addition to the texts of the document to be registered; and

upon retrieval of the document containing the designated search term, executing first a component character table search for thereby extracting those documents which contain all species of characters constituting any one of said search terms designated by the operator by consulting said component character table;

executing subsequently a condensed text search by consulting the condensed texts of the documents extracted through said component character table search for extracting only the documents corresponding to the condensed texts which contain all the fragmental character strings constituting any one of said search terms designated by the operator to thereby select the documents containing the designated search terms; and

executing finally a text body search for extracting a document which satisfies query condition imposed on said search terms by consulting the texts of the documents extracted through said component character table search and said condensed text search.

15. A document data processing method for retrieving a document containing at least a search term designated by an operator from a document database registering therein document information in terms of character code data while referring to textual content of said document, comprising steps of:

upon registration of text documents in said document database,

creating condensed texts by decomposing each of textual character strings of the documents to be registered into fragmental character strings in dependence on character species each of the fragmental character strings being able to include one of katakana character string, hiragana character string, kanji character string, alphabetic character string, numeric character string and symbol character string, and checking mutual inclusion relations possibly existing among said fragmental character strings resulting from said decomposition, while checking said hiragana character string by consulting a basic word dictionary and conjunction rules as to whether said hiragana character string represents a succession of subsidiary words having semantically no meaning as the search term, to thereby create the condensed texts each constituted by a set of the fragmental character strings in which any character string found to be included by other character string and any hiragana character string found to be a succession of the semantically meaningless subsidiary words are excluded;

creating a component character table in which characters occurring in registered texts are registered without duplication; and

registering in said document database said condensed texts together with said component character table in addition to the texts of the document to be registered; and

upon retrieval of the document containing the designated search term, executing first a component character table search for thereby extracting those documents which contain all species of characters constituting the search term designated by the operator by consulting said component character table;

executing subsequently a condensed text search by consulting the condensed texts of the documents extracted through said component character table search for extracting only the documents corresponding to the condensed texts which contain the fragmental character strings constituting the search term unless said fragmental character strings have been determined to be a succession of semantically meaningless words as the search term after the check of said fragmental character strings by using the basic word dictionary and the conjunction rules; and

executing finally a text body search for extracting a document which satisfies query condition imposed on the search term by consulting the texts of the documents extracted through said component character table search and said condensed text search while consulting the registered texts of the documents extracted through said component character table search when any one of said fragmental character strings has been determined to be a succession of the semantically meaningless words, for thereby extracting a document which contains each of the fragmental character strings and which satisfies the retrieval condition imposed on the search term concerning the positional relation thereof.

16. A document data processing method for document retrieval according to claim 15, wherein said text body search is executed when said search term is constituted with a plurality of character species and when said query condition includes a positional condition of the search term in the next text.

17. A document data processing method for retrieving a document containing at least a search term designated by an operator from a document database registering therein document information in terms of character code data while referring to textual content of said document, comprising steps of:

upon registration of text documents in said document database,

creating condensed texts by decomposing each of textual character strings of the documents to be registered into fragmental character strings in dependence on character species each of the fragmental character strings being able to include one of katakana character string, hiragana character string, kanji character string, alphabetic character string, numeric character string and symbol character string, and checking mutual inclusion relations possibly existing among said fragmental character strings resulting from said decomposition, after having eliminated all the hiragana character strings, to thereby create the condensed texts each constituted by a set of the fragmental character strings in which any character string found to be included by other character string is excluded;

creating a component character table in which characters occurring in registered texts are registered without duplication; and

registering in said document database a plurality of said condensed texts corresponding to said character species, respectively, together with said component character table in addition to the texts of the documents to be registered; and

upon retrieval of the document containing the designated search term, executing first a component character table search for thereby extracting those documents which contain all species of characters constituting the search term designated by the operator by consulting said component character table;

executing subsequently a condensed text search by consulting the condensed texts of the documents extracted through said component character table search for extracting only the documents corresponding to the condensed texts which contain the fragmental character strings constituting the search term designated by the operator provided that said fragmental character strings constituting the search term designated by the operator has been determined as including none of the hiragana character strings as a result of corresponding decision step; and

executing finally a text body search for extracting a document which satisfies query condition imposed on the search term by consulting the texts of the documents extracted or alternatively for extracting a document containing the designated fragmental character strings and satisfying said query condition by consulting the original text of the document extracted through said component character table search.

18. A document data processing method for document retrieval according to claim 17, wherein said text body search is executed when said search term is constituted with a plurality of character species and when said query condition includes a positional condition of the search term in the next text.

19. A document data processing method for retrieving a document containing at least a search term designated by an operator from a document database registering therein document information in terms of character code data while referring to textual content of said document, comprising steps of:

upon registration of text documents in said document database,

creating condensed texts by decomposing each of textual character strings of the documents to be registered into fragmental character strings on the basis of at least one of character species including katakana character, hiragana character, kanji character, alphabetic character, numeric character and symbol character and checking mutual inclusion relations possibly existing among said fragmental character strings resulting from said decomposition, to thereby create a plurality of condensed texts separately on a character species basis, each of said condensed texts being constituted by the fragmental character strings of a same character species while excluding any character string found to be included by other character string;

creating a component character table describing the species of the characters occurring in registered texts;

registering in said document database said plurality of character-species based condensed texts together with said component character table in addition to the text of the document to be registered; and

upon retrieval of the document containing the designated search term, executing first a component character table search for thereby extracting those documents which contain all the species of characters constituting the search term designated by the operator by consulting said component character table;

executing subsequently a condensed text search by consulting the condensed text corresponding to the character species of the fragmental character strings constituting the search term designated by the operator in the documents extracted through said component character table search for extracting only the documents corresponding to the condensed texts which contain the fragmental character strings constituting the search term designated by the operator to thereby select the documents containing the designated search term; and

executing finally a text body search for extracting a document which satisfies query condition imposed on the search term by consulting the texts of the documents extracted through said component character table search and said condensed text search.

20. A document data processing method for document retrieval according to claim 19, wherein said text body search is executed when said search term is constituted with a plurality of character species and when said query condition includes a positional condition of the search term in the next text.

21. A document data processing method for retrieving a document containing a search term designated by an operator from a document database registering therein document information in terms of character code data while referring to textual content of said document, comprising steps of:

upon registration of text documents in said document database,

creating condensed texts by decomposing each of textual character strings of the documents to be registered into fragmental character strings on the basis of at least one of character species including katakana character, hiragana character, kanji character, alphabetic character, numeric character and symbol character and checking mutual inclusion relations possibly existing among said fragmental character strings resulting from said decomposition, to thereby create the condensed texts each constituted by a set of the fragmental character strings in which any character string found to be included by other character string is eliminated;

creating a component character table in which characters occurring in each of said condensed texts are registered without duplication; and

registering in said document database said condensed texts together with said component character table in addition to the text of the document to be registered; and

upon retrieval of the document containing the designated search term, executing first a component character table search for thereby extracting those documents which contain all species of characters constituting the search term designated by the operator by consulting said component character table; and

executing subsequently a condensed table search by consulting the condensed texts of the documents extracted through said component character table search for thereby extracting only the documents corresponding to the condensed texts which contain the fragmental character strings constituting the search term designated by the operator to thereby extract the documents containing the designated search term;

creating a component character table in which characters occurring in texts are registered without duplication; and

registering in said document database said component character table in addition to the texts of the documents to be registered; and

upon retrieval of the document containing the designated search term, executing first a component character table search for thereby extracting those documents which contain all species of characters constituting the search term designated by the operator by consulting said component character table; and

executing subsequently a text body search by consulting the texts of the documents extracted through said component character table search for thereby extracting only the document which contains the designated search term and which satisfies query condition imposed on the search term such as positional relation thereof in the text, whereby a full text retrieval is carried out at an equivalently increased speed.

22. A document data processing method for retrieving a document containing a search term designated by an operator from a document database registering therein document information in terms of character code data while referring to textual content of said document, comprising the steps of:

upon registration of text documents in said document database,

creating a component character table in which characters occurring in texts are registered without duplication; and

registering in said document database said component character table in addition to the texts of the documents to be registered; and

upon retrieval of the document containing the designated search term,

executing first a component character table search for thereby extracting those documents which contain all species of characters constituting the search term designated by the operator by consulting said component character table; and

executing subsequently a text body search by consulting the texts of the documents extracted through said component character table search for thereby extracting only the document which contains the designated search term and which satisfies query condition imposed on the search term.

23. A document data processing method for retrieving a document containing at least a search term designated by an operator from a document database registering therein document information in terms of character code data while referring to textual content of said document, comprising steps of:

upon registration of text documents in said document database,

creating condensed texts by decomposing each of textual character strings of the documents to be registered into fragmental character strings on the basis of at least one of character species including katakana character, hiragana character, kanji character, alphabetic character, numeric character and symbol character and checking mutual inclusion relations possibly existing among said fragmental character strings resulting from said decomposition, to thereby create the condensed texts each constituted by a set of the fragmental character strings in which any character string found to be included by other character string is eliminated; and

registering in said document database said condensed texts in addition to the texts of the documents to be registered; and

upon retrieval of the document containing the designated search term, executing a condensed text search by consulting the condensed texts of the documents for extracting only the documents corresponding to the condensed texts which contain the fragmental character strings constituting the search term designated by the operator to thereby select the documents containing the designated search term; and

executing a text body search for extracting a document which satisfies query condition imposed on the search term by consulting the texts of the documents extracted through said condensed text search.

24. A document data processing method for document retrieval according to claim 23, wherein said text body search is executed when said search term is constituted with a plurality of character species and when said query condition includes a positional condition of the search term in the next text.

25. A document data processing system for retrieving a document containing a search term designated by an operator from a document database registering therein document information in terms of character code data while referring to textual content of said document, comprising:

for registration of text documents in said document database,

means for creating condensed texts by decomposing each of textual character strings of the documents to be registered into fragmental character strings on the basis of at least one of character species including include hiragana character, kanji character, alphabetic character, numeric character and symbol character and checking mutual inclusion relations possibly existing among said fragmental character strings resulting from said decomposition, to thereby create the condensed texts each constituted by a set of the fragmental character strings in which any character string found to be included by other character string is eliminated;

means for creating a component character table in which characters occurring in each of said condensed texts are registered without duplication; and

means for registering in said document database said condensed texts together with said component character table in addition to the texts of the documents to be registered; and

for document retrieval,

component character table search means for extracting those documents which contain all species of characters constituting the search term designated by the operator by consulting said component character table;

condensed text search means for extracting only the documents corresponding to the condensed texts which contain the fragmental character strings constituting the search term designated by the operator by consulting the condensed texts of the documents extracted through the component character table search; and

text body search means for extracting a document which satisfies query condition imposed on the search term by consulting the texts of the documents extracted.

26. A document data processing system for retrieving a document containing a search term designated by an operator from a document database registering therein document information in terms of character code data while referring to textual content of said document, comprising:

for registration of text documents in said document database,

means for creating condensed texts by decomposing each of textual character strings of the documents to be registered into fragmental character strings on the basis of at least one of character species including include hiragana character, kanji character, alphabetic character, numeric character and symbol character and checking mutual inclusion relations possibly existing among said fragmental character strings resulting from said decomposition, to thereby create the condensed texts each constituted by a set of the fragmental character strings in which any character string found to be included by other character string is eliminated;

means for creating a component character table in which characters occurring in each of said condensed texts are registered without duplication;

means for registering in said document database said condensed texts together with said component character table in addition to the texts of the documents to be registered; and

means for storing the condensed text data in a RAM disk while storing the component character table in a semiconductor memory; and

for document retrieval,

component character table search means for extracting those documents which contain all species of characters constituting the search term designated by the operator by consulting said component character table;

condensed text search means for extracting only the documents corresponding to the condensed texts which contain the fragmental character strings constituting the search term designated by the operator by consulting the condensed texts of the documents extracted through the component character table search; and

text body search means for extracting a document which satisfies query condition imposed on the search term by consulting the texts of the documents extracted.

27. A document data processing system for retrieving a document containing a search term designated by an operator from a document database registering therein document information in terms of character code data while referring to textual content of said document, comprising:

for registration of text documents in said document database,

means for creating condensed texts by decomposing each of textual character strings of the documents to be registered into fragmental character strings on the basis of at least one of character species including include hiragana character, kanji character, alphabetic character, numeric character and symbol character and checking mutual inclusion relations possibly existing among said fragmental character strings resulting from said decomposition, to thereby create the condensed texts each constituted by a set of the fragmental character strings in which any character string found to be included by other character string is eliminated;

means for creating a component character table in which characters occurring in each of said condensed texts are registered without duplication; and

means for registering in said document database said condensed texts together with said component character table in addition to the texts of the documents to be registered and storing the text data and the condensed text data in a magnetic disk while storing said component character table in a semiconductor memory; and

for document retrieval,

component character table search means for extracting those documents which contain all species of characters constituting the search term designated by the operator by consulting said component character table;

means for checking the number of the documents extracted through the component character table search;

condensed text search means for reading out all of said condensed texts by neglecting the result of the component character table search, when said number of said extracted documents has attained a predetermined number, to thereby extract only the documents corresponding to the condensed texts which contain the fragmental character strings constituting the search term designated by the operator, while consulting the condensed texts of the documents extracted through said component character table search to thereby extract only the documents corresponding to the condensed text containing the fragmental character strings which-constitute the search term designated by the operator, when said number of said extracted documents is smaller than said predetermined number; and

text body search means for extracting a document which satisfies query condition imposed on the search term by consulting the texts of the documents extracted.

28. A document data processing system for retrieving a document containing a search term designated by an operator from a document database registering therein document information in terms of character code data while referring to textual content of said document, comprising:

for registration of text documents in said document database,

means for creating condensed texts by decomposing each of textual character strings of the documents to be registered into fragmental character strings on the basis of at least one of character species including include hiragana character, kanji character, alphabetic character, numeric character and symbol character and checking mutual inclusion relations possibly existing among said fragmental character strings resulting from said decomposition, to thereby create the condensed texts each constituted by a set of the fragmental character strings in which any character string found to be included by other character string is eliminated;

means for creating a component character table in which characters occurring in each of said condensed texts are registered without duplication; and

means for registering in said document database said condensed texts together with said component character table in addition to the texts of the documents to be registered and storing the text data and the condensed text data in a magnetic disk while storing said component character table in a semiconductor memory; and

for document retrieval,

component character table search means for extracting those documents which contain all species of characters constituting the search term designated by the operator by consulting said component character table;

means for checking the number of the documents extracted through the component character table search;

condensed text search means for reading out all of said condensed texts by neglecting the result of the component character table search only when said number of said extracted documents has attained a predetermined number, to thereby extract only the documents corresponding to-the condensed texts which contain the fragmental character strings constituting the search term designated by the operator; and

text body search means for extracting a document which satisfies query condition imposed on the search term by consulting the texts of the documents extracted, while consulting the condensed texts of the documents extracted through said component character table search to thereby extract only the document corresponding to the condensed text containing the fragmental character strings which constitute the search term designated by the operator, when said number of said extracted documents is smaller than said predetermined number.

29. A document data processing method for retrieving a document containing at least a search term designated by an operator from a document database registering therein document information in terms of character code data while referring to textual content of said document, comprising steps of:

upon registration of text documents in said document database,

creating condensed texts by decomposing each of textual character strings of the documents to be registered into fragmental character strings on the basis of at least one of character species including hiragana character, katakana character, kanji character, alphabetic character, numeric character and symbol character and checking mutual inclusion relations possibly existing among said fragmental character strings resulting from said decomposition, to thereby create the condensed texts each constituted by a set of the fragmental character strings in which any character string found to be included by other character string is eliminated;

creating a concatenated component character table by preparing, for each of the documents, information of all usable character strings each composed of at least two characters, said information including first information indicating those character strings which are used in the document to be registered and second information indicating those character strings unused in the document to be registered; and

registering in said document database said condensed texts together with said concatenated component character table in addition to the texts of the document to be registered; and

upon retrieval of the document containing the designated search term,

executing a component character table search for extracting all the documents in which all the character strings contained in the search term designated by the operator and each composed of at least two characters are used, by consulting said concatenated component character table;

executing a condensed text search by consulting the condensed texts corresponding to the documents extracted through said component character table search for thereby extracting only the documents which contain the fragmental character strings constituting the search term designated by the operator; and

executing finally a text body search for extracting a document from the documents selected through said condensed text search which document satisfies query condition imposed on the search term by consulting the texts of the documents extracted through said concatenated component character table search and said condensed text search.

30. A document data processing method for document retrieval according to claim 29, wherein in association with said concatenated component character table a bit list in which one-bit information are allocated to all usable character strings each composed of at least two characters, respectively, is prepared for each of said documents and wherein bit positions in said bit list for the character strings used in the documents are set to "1s", respectively, while the bit positions for the character strings not used in the documents are set to "0s", respectively.

31. A document data processing method for document retrieval according to claim 30, wherein said concatenated component character table is prepared on the basis of the individual character strings each constituted by a predetermined number n (where n is an integer greater than or equal to 2) of characters for each character species including hiragana character, katakana character, kanji character, numeric character, symbol character and symbol character.

32. A document data processing method for document retrieval according to claim 30, wherein said concatenated component character table is prepared by mapping sets of character codes to the bit list having a number of entries which is smaller than the number of combinations of the characters used actually by using a hash function.

33. A document data processing method for document retrieval according to claim 32, wherein each of the character strings used actually is decomposed on the basis of at least one of the character species including hiragana character, katakana character, kanji character, alphabetic character, numeric character, symbol and symbol character, and wherein said concatenated component character table is prepared by mapping sets of character codes to the bit list having a number of entries which is smaller than the number of combinations of the characters used actually by using a hash function.

34. A document data processing method for document retrieval according to claim 32, wherein use frequencies at which the character strings are actually used are checked, and upon mapping the sets of character codes to the bit list having a number of bits smaller than the number of the character strings used actually by the hash function, the character strings of a lower use frequency are mapped to a same bit.

35. A document data processing method for document retrieval according to claim 32, wherein the character codes are mapped to a number of codes of entries which is smaller than that of the characters used actually by using said hash function, whereon sets of the hashed character codes are mapped to the bit list having a number of entries smaller than the number of the actually used character strings by using another hash function.

36. A document data processing method for document retrieval according to claim 30, said concatenated component character table being prepared on the basis of the character strings each composed of n characters, wherein in the step of the concatenated component character table search, the document containing all the character strings each composed of n characters and contained without duplication in the search term designated by the operator is extracted by searching the bit list having the relevant bit positions all set to 1".

37. A document data processing method for document retrieval according to claim 30, said concatenated component character table being prepared on the basis of the character strings each composed of n characters, wherein in the step of the concatenated component character table search, the document containing all the character strings each composed of n characters and contained in duplication in the search term designated by the operator is extracted by searching the bit list having the relevant bit positions all set to "1".

38. A document data processing method for document retrieval according to claim 30, said concatenated component character table being constituted by character strings each composed of a given number of characters in a range of one to n, wherein when the search term designated by the operator is composed of a number of characters which is smaller than n, the result of said concatenated component character table search is outputted as the final result of the document retrieval, whereupon the search processing is ended.

39. A document data processing method for document retrieval according to claim 29, wherein said text body search is executed when said search term is constituted with a plurality of character species and when said query condition includes a positional condition of the search term in the next text.

40. A document data processing method for retrieving a document containing at least a search term designated by an operator from a document database registering therein document information in terms of character code data while referring to textual content of said document, comprising steps of:

upon registration of text documents in said document database,

creating condensed texts by decomposing each of textual character strings of the documents to be registered into fragmental character strings on the basis of at least one of character species including hiragana character, katakana character, kanji character, alphabetic character, numeric character and other symbol character and checking mutual inclusion relations possibly existing among said fragmental character strings resulting from said decomposition, to thereby create the condensed texts each constituted by a set of the fragmental character strings in which any character string found to be included by other character string is eliminated;

creating a single component character table and a concentrated component character table by preparing, for each of the documents, information of all usable single characters and character strings each composed of at least two characters, said information including first information indicating those single-character and character strings which are used in the document to be registered and second information indicating those single-character and character strings unused in the document to be registered, respectively; and

registering in said document database said condensed texts together with said concatenated component character table in addition to the texts of the document to be registered; and

upon retrieval of the document containing the designated search term,

executing a component character table search for extracting all the documents in which all the character strings contained in the search term designated by the operator and each composed of at least two characters are used, by consulting said concatenated component character table;

executing a condensed text search by consulting the condensed texts corresponding to the documents extracted through said component character table search for thereby extracting only the documents which contain the fragmental character strings constituting the search term designated by the operator; and

executing finally a text body search for extracting a document from the documents selected through said condensed text search which document satisfies query condition imposed on the search term by consulting the texts of the documents extracted through said concatenated component character table search and said condensed text search.

41. A document data processing method for document retrieval according to claim 40, wherein in association with said concatenated component character table, a bit list in which one-bit information are allocated to all usable character strings each composed of at least two characters, respectively, is prepared for each of said documents and wherein bit positions in said bit list for the character strings used in the documents are set to "1s", respectively, while the bit positions for the character strings not used in the documents are set to "0s", respectively.

42. A document data processing method for document retrieval according to claim 40, wherein said text body search is executed when said search term is constituted with a plurality of character species and when said query condition includes a positional condition of the search term in the next text.

43. A text data creating method for creating a text database for storing document information as character code data, comprising steps of:

(1) fetching text data;

(2) determining frequencies at which individual character strings each constituted by a predetermined number n of characters are used in the text data and rearraying said character strings in a sequential order in dependence on said frequencies;

(3) establishing correspondences between said character strings and a number of entries which is smaller than the number of said character strings and storing said correspondences in the form of a hash table; and

(4) storing at the entry corresponding to the character strings used in said text data said character strings in the form of a componeht character table.

44. A full text retrieval method for retrieving a document containing a search term designated by an operator from a text data database registering therein document information as character code data while referring to textual content of said document, comprising steps of:

(1) fetching text data;

(2) determining frequencies at which individual character strings each constituted by a predetermined number n of characters are used in the text data and rearraying said character strings in a sequential order in dependence on said frequencies;

(3) establishing correspondences between said character strings and a number of entries which is smaller than the number of said character strings and storing said correspondences in the form of a hash table;

(4) storing at the entry corresponding to the character strings used in said text data said character strings in the form of a component character table;

(5) decomposing the search term designated by the operator into fragmental character strings each composed of n characters;

(6) extracting from said component character table those entries which correspond to said fragmental character strings resulting from said decomposition; and

(7retrieving said document in which all the character strings constituting said search terms exist, by consulting the entries extracted from said component character table.

45. A document data processing system for retrieving a document containing a search term designated by an operator from a document database registering therein document information in terms of character code data while referring to textual content of said document, comprising:

for registration of text documents in said document database,

means for registering texts of documents to be registered;

means for creating condensed texts by decomposing each of textual character strings of the documents to be registered into fragmental character strings on the basis of at least one of character species including hiragana character, katakana character, kanji character, alphabetic character, numeric character and symbol character and checking mutual inclusion relations possibly existing among said fragmental character strings resulting from said decomposition, to thereby create and register the condensed texts each constituted by a set of the fragmental character strings in which any character string found to be included by-other character string is eliminated; and

means for creating a concatenated component character table by preparing, for each of the documents, information of all usable character strings each composed of at least two characters, said information including first information indicating those character strings which are used in the document to be registered and second information indicating those character strings unused in the document to be registered and registering said concatenated component character table in said database; and

for retrieval of the document containing the designated search term,

component character table search means for extracting all the documents in which all the character strings contained in the search term designated by the operator and each composed of at least two characters are used, by consulting said concatenated component character table;

condensed text search means for executing a condensed text search by consulting the condensed texts corresponding to the documents extracted through said component character table search for thereby extracting only the documents which contain the fragmental character strings constituting the search term designated by the operator; and

text body search means for executing a text body search for extracting a document from the documents selected through said condensed text search which document satisfies query condition imposed on the search term by consulting the texts of the documents extracted through said concatenated component character table search and said condensed text search.

46. A document data processing system for retrieving a document containing a search term designated by an operator from a document database registering therein document information in terms of character code data while referring to textual content of said document, comprising:

for registration of text documents in said document database,

means for registering texts of documents to be registered;

means for creating condensed texts by decomposing each of textual character strings of the documents to be registered into fragmental character strings on the basis of at least one of character species including hiragana character, katakana character, kanji character, alphabetic character, numeric character and symbol character and checking mutual inclusion relations possibly existing among said fragmental character strings resulting from said decomposition, to thereby create and register the condensed texts each constituted by a set of the fragmental character strings in which any character string found to be included by other character string is eliminated;

means for creating a hash table by checking frequencies at which said fragmental character strings are used, determining a hash function on the basis of the frequency information and mapping said fragmental character strings to a bit list having entries in a number smaller than that of combinations of actually used character; and

means for creating a concatenated component character table by preparing, for each of the documents, information of all usable character strings each composed of at least two characters by consulting said hash table, said information including first information indicating those character strings which are used in the document to be registered and second information indicating those character strings unused in the document to be registered and registering said concatenated component character table in said database; and

for retrieval of the document containing the designated search term,

component character table search means for extracting all the documents in which all the character strings contained in the search term designated by the operator and each composed of at ieast two characters are used, by consulting said concatenated component character table;

condensed text search means for executing a condensed text search by consulting the condensed texts corresponding to the documents extracted through said component character table search for thereby extracting only the documents which. contain the fragmental character strings constituting the search term designated by the operator; and

text body search means for executing a text body search for extracting a document from the documents selected through said condensed text search which document satisfies query condition imposed on the search term by consulting the texts of the documents extracted through said concatenated component character table search and said condensed text search.

47. An index creating apparatus, comprising:

means for fetching data for retrieval;

counting means for determining frequencies at which characters contained in said data for retrieval are used;

sorting means for rearraying said characters in the order of frequencies at which said characters are used;

means for establishing correspondences between said characters and a number of bits, respectively, said bit number being smaller than that of said characters,

means for converting character codes of said characters to the corresponding bits; and

means for manipulating said bits on a bit-by-bit basis.

48. A document retrieval apparatus, comprising:

input means for inputting a search term;

means for extracting bit lists corresponding to character strings constituting said search term from a component character table;

means for logically ANDing said bit lists; and

means for transforming result of said ANDing operation into a document identifier affixed to a document.

49. A document data processing method for retrieving a document containing a search term designated by an operator from a document database registering therein document information in terms of character code data while referring to the textual content of said document, comprising steps of:

upon registration of text documents in said document database, creating a concatenated component character table in which character strings, each being constituted with n-characters (n<

2) and occurring in the text documents, are registered without duplication for each of the text documents, and registering in said document database said component character table in addition to the texts of the documents to be registered; and

upon retrieval of a document containing the designated search term, executing first a component character table search for thereby extracting those documents which contain all species of characters constituting the search term designated by the operator by consulting said concatenated component character table; and

executing subsequently a text body search by consulting the texts of the documents extracted through said component character table search for thereby extracting only the document which contains the designated search term and which satisfies a query condition imposed on the search term.

50. A document data processing method for document retrieval according to claim 49, further including, upon registration of the text documents, a step of creating and registering an additional character table in which characters occurring in the text documents or character strings, each being constituted with characters of a number smaller than n and occurring in the text documents, are registered, wherein said additional character table is consulted instead of said concatenated character table when said search term is constituted with characters of a number smaller than n.