Abstract:
Sequentially input new document information is sorted and retained in a proper folder to facilitate search and retrieval of a desired document to follow. To this end, a list of proper candidate folders is presented to a user to support user saving works. Discrimination between proper folders is made precise by using a search condition, to thereby make search of a desired document easy and reliable.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to searching desired information from a plurality of sets of information.  
           [0003]    The present invention also relates to sorting information into specific types and holding it for the management of a plurality set of information.  
           [0004]    The present invention also relates to collecting electronic documents used for electronic newspapers, electronic publishing, electronic circulars and the like and to managing collected documents.  
           [0005]    2. Related Background Art  
           [0006]    Conventional document processing systems enumerate newly arrived documents which a user peruses and collects necessary documents. As a storage device for collected documents, a folder is used. A user selects one of enumerated folders to store the collected document therein. In using stored documents, a user selects the folder storing a desired document and accesses the desired document. Folders are structured hierarchically so that a user can search documents easily.  
           [0007]    In using such a document processing system, documents belonging to the same field as viewed from a user specific point are stored in the same folder. In using stored documents, a user selects a desired folder from the specific viewpoint to obtain a desired document.  
           [0008]    Other document processing systems which manage documents without using folders are database management systems which search a document by using document attributes, information retrieval systems which search a document by using document keywords, full text retrieval systems which search a document by using search words from the text of the document, and other systems.  
           [0009]    The above-described conventional systems are, however, associated with some problems of lower efficiencies of document collection and use because it is difficult to find a desired folder for document collection and use. This problem occurs when a number of folders are used. It is difficult to find a proper folder from a list of a plurality of enumerated folders. This problem can be solved more or less by hierarchically holding folders. However, a user specific viewpoint for documents often changes with time so that the hierarchical structure formed in the past may mismatch the present user specific viewpoint. Therefore, it becomes difficult to trace the hierarchical structure and find a desired folder. In another case, if a long time elapses after a folder is used, a user often forgets information about that folder or the presence of the folder itself. Also in this case, it is difficult to find the folder. As it becomes difficult to find a proper folder, the number of folders in which a collected document is stored may become small, the collected document may be stored in an improper folder, the collected document may be stored less in a plurality of folders, or the collected document may not be stored. In such cases, the folder cannot reflect correctly the user specific viewpoint), and it becomes difficult to find a desired document from folders.  
           [0010]    For the management of documents by using database management systems or information retrieval systems, it is necessary to provide documents with attributes or keywords each time documents are collected so that a load of collection work becomes high. A high load of collection work poses significant problems because such document processing systems are used daily by individual persons.  
           [0011]    Document search from user specific viewpoints is therefore difficult in the case of database management systems and information retrieval systems using only attributes and keywords assigned to documents and in the case of document management using full text retrieval systems.  
         SUMMARY OF THE INVENTION  
         [0012]    It is an object of the present invention to manage documents from specific user viewpoints and facilitate proper document collection and use.  
           [0013]    It is another object of the invention to facilitate selection of a proper set of information in which newly input information is held.  
           [0014]    It is another object of the present invention to facilitate searching information which matches desired search conditions.  
           [0015]    It is another object of the present invention to make coincidence judgment of search conditions more proper. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    [0016]FIG. 1 is a block diagram showing an example of the functional structure for information collection and search.  
         [0017]    [0017]FIG. 2 is a diagram showing a hardware structure of a document processing system of this invention.  
         [0018]    [0018]FIG. 3 is a flow chart illustrating the outline of a candidate folder search process of this invention.  
         [0019]    [0019]FIG. 4 is a flow chart illustrating the outline of a document retaining process of this invention.  
         [0020]    [0020]FIG. 5 is a flow chart illustrating the outline of a folder search process of the invention.  
         [0021]    [0021]FIG. 6 is a block diagram showing an example of the functional structure for information collection.  
         [0022]    [0022]FIG. 7 is a block diagram showing an example of the functional structure for information search.  
         [0023]    [0023]FIG. 8 is a block diagram showing an example of a functional structure for sorting a plurality piece of information into one specific type.  
         [0024]    [0024]FIG. 9 is a flow chart illustrating a document sorting process used for the functional structure shown in FIG. 8.  
         [0025]    [0025]FIG. 10 is a block diagram showing another example of the functional structure for information collection and search.  
         [0026]    [0026]FIG. 11 is a block diagram showing a functional structure for the calculation of a search score.  
         [0027]    [0027]FIG. 12 is a flow chart illustrating the outline of a search score calculating process.  
         [0028]    [0028]FIG. 13 is a diagram showing an example of a document set retainer.  
         [0029]    [0029]FIG. 14 is a flow chart illustrating a second example of the outline of the search score calculating process.  
         [0030]    [0030]FIG. 15 is a diagram showing a second example of the document set retainer.  
         [0031]    [0031]FIG. 16 is a diagram illustrating a load state of control programs of the invention into a computer.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0032]    Embodiments of the invention will be described in detail with reference to the accompanying drawings.  
         [0033]    [0033]FIG. 1 is a block diagram showing the functional structure for information collection and search of this invention.  
         [0034]    In FIG. 1, reference numeral 101 represents a folder/document retainer for retaining folders and documents belonging to each folder. Reference numeral  102  represents a new document retainer for retaining a newly arrived document. Reference numeral  103  represents a candidate folder searcher for searching a candidate folder suitable for retaining the document retained by the new document retainer  102 . Reference numeral  104  represents a candidate folder retainer for retaining a candidate folder searched by the candidate folder searcher  103 . Reference numeral  105  represents a selected folder retainer for retaining the folder selected by a user from candidate folders retained by the candidate folder retainer  104 . Reference numeral  106  represents a saving processor for controlling the folder/document retainer  101  to retain the document retained by the new document retainer  102  in the selected folder retained by the selected folder retainer  105 . Reference numeral  107  represents a search condition retainer for retaining search conditions of each folder. Reference numeral  108  represents a folder searcher for searching folders retained in the folder/document retainer  101  in accordance with the search condition retained by the search condition retainer  107 . Reference numeral  109  represents a search result retainer for retaining the folder searched by the folder searcher  108 .  
         [0035]    [0035]FIG. 2 is a diagram showing the hardware structure of a document processing system of this invention. In FIG. 2, reference numeral  202  represents a CPU which operates in accordance with programs stored in a ROM  203 .  
         [0036]    Reference numeral  202  represents a RAM which provides storage areas necessary for the operations of the new document retainer  102 , candidate folder retainer  104 , selected folder retainer  105 , search condition retainer  107 , search result retainer  109 , and the above-described programs. The programs stored in ROM  203  executes procedures illustrated in the flow charts to be described later. Reference numeral  104  represents a disk drive which realizes the folder/document retainer  101 . Reference numeral  205  represents a bus. Reference numeral  206  represents a display such as a CRT and a liquid crystal display for displaying characters, images and the like. Reference numeral  207  represents an input device such as a keyboard and a pointing device.  
         [0037]    In this example, the folder/document retainer  101  stores a list of documents and a list of folders. A document d is given by: 
           d= ( t, v ( d )) 
         [0038]    where t is text data of a document, and v(d) is vector data representing the feature of a text t related to a vector space model. A folder f is given by: 
           f= (1,  D, v ( f )) 
         [0039]    where 1 is label data represented by a character string by which a user visually confirms a folder. This character string may be input from the input device  207  by a user or may be automatically allocated. The data D represents a set of documents retained in a folder and may represent an empty folder. The data v(f) is vector data (dεD) which is an average of vectors v(d) of all documents d retained in a folder f. The number of folders retained in the folder/document retainer  101  is represented by N. The new document retainer  102  retains one document. The candidate folder retainer  104 , selected folder retainer  105 , and search result retainer  109  each have a list of folder numbers. The search condition retainer  107  retains search words and search equations representing logical relationship between search words.  
         [0040]    With reference to the flow chart shown in FIG. 3, the operation of a candidate folder search process of the document processing system of the invention will be described.  
         [0041]    At Step S 301  it is checked whether the new document retainer  102  has retained the text t(n) of a newly arrived document. If retained, the flow advances to Step S 302 , whereas if not, Step S 301  is repeated until the new document retainer  102  retains the text t(n) of a new document. The text t(n) of a new document arrives at the new document retainer  102  at a timing of an input instruction by a user or at a timing of automatic supply of a text from a text supplier.  
         [0042]    At Step S 302  a feature vector v(dn) of the text t(n) is generated, this feature vector and the text t(n) being retained by the new document retainer  102 . Thereafter, the flow advances to Step S 303 .  
         [0043]    At Step S 303  the value x of a counter is initialized to 1. The counter is used for counting a folder number and sequentially accessing folder information retained by the folder/document retainer  101 . Thereafter, the flow advances to Step S 304 .  
         [0044]    At Step S 304  the value x of the counter is compared with the number N of folders retained in the folder/document retainer  101  in order to judge whether the processes of Steps S 305  to S 307  have been executed for all folders retained by the folder/document retainer  101 . If x≦N, the flow advances to Step S 305 , whereas if x&gt;N, the candidate folder search process illustrated in the flow chart of FIG. 3 is terminated.  
         [0045]    At Step S 305  a score S=g(v(dn), v(fx)) is calculated where f(x) is the x-th folder retained by the folder/document retainer  101  and d(n) is a new document. The function g is used for determining a similarity of documentary features between the new document d(n) and the folder f(x). The smaller this score, the more similar the features of the new document d(n) are so that the folder is suitable for retaining the new document. The function q is given by: 
           g ( v ( 1 ),  v ( 2 ))=( v ( 1 )· v ( 2 ))/(| v ( 1 )|| v ( 2 )|) 
         [0046]    After the score is calculated, the flow advances to Step S 306 .  
         [0047]    At Step S 306  the candidate folder retainer  104  retains the score S calculated at Step S 305  and the corresponding folder number x in an ascending order of values of S. Thereafter, the flow advances to Step S 307 .  
         [0048]    At Step S 307  the value x of the counter is incremented by 1 and thereafter the flow returns to Step S 304 .  
         [0049]    Information (folder label and the like) regarding the candidate folder obtained by the candidate folder search process described with reference to the flow chart of FIG. 3 and retained in the candidate folder retainer  104 , is displayed on the display  206  in correspondence with the document retained by the new document retainer  102 , to thereby notify the candidate folder to the user.  
         [0050]    Folders displayed on the display  206  in the retained order (ascending order of score S) may include all folders retained by the candidate folder retainer  104  or only upper level folders selected in accordance with the score S and the number N.  
         [0051]    Next, with reference to the flow chart shown in FIG. 4, the operation of a document retaining process of the document processing system of this invention will be described.  
         [0052]    At Step S 401  it is checked whether the selected folder retainer  105  has retained a folder list F. If retained, the flow advances to Step S 402 , whereas if not, Step S 401  is repeated until the selected document retainer  105  retains the list F. This list F is a train of folders input by the user from the input device  207  such as a keyboard. The list F is input while considering candidate folder information supplied from the candidate folder retainer  104 .  
         [0053]    At Step S 402  the value x of a counter is initialized to 1, the counter being used for indicating the sequential order of the accessing folder in the list F. Thereafter, the flow advances to Step S 403 .  
         [0054]    At Step S 403 , the value x of the counter is compared with the number |F| of folders. If x≦|F|, the flow advances to Step S 404 , whereas if x&gt;|F|, the document retaining process illustrated in the flow chart of FIG. 4 is terminated.  
         [0055]    At Step S 404 , the new document d(n) is added to a document list D(Fx) corresponding to the x-th folder f(Fx) in the selected folder retainer  105 . For the new D(Fx) added with d(n), a new vector v(f(Fx)) is calculated which is an average of vectors v(d) (d εD(Fx)). Thereafter, the flow advances to Step S 405 .  
         [0056]    At Step S 405 , the value x of the counter is incremented by 1 and thereafter the flow returns to Step S 403 .  
         [0057]    Next, with reference to the flow chart shown in FIG. 5, the operation of a folder search process of the document processing system of this invention will be described.  
         [0058]    At Step S 501  it is checked whether the search condition retainer  107  has retained a search condition c. If retained, the flow advances to Step S 502 , whereas if not, Step S 501  is repeated until the search condition retainer  107  retains the search condition c. The search condition c is a train of words or sentences input by the user from the input device  207  such as a keyboard.  
         [0059]    At Step S 502  the value x of a counter is set to a default value 1, the counter being used for indicating the sequential order of the accessing folder among all folders retained in the folder/document retainer  101 . Thereafter, the flow advances to Step S 503 .  
         [0060]    At Step S 503 , the value x of the counter is compared with the total number N of folders retained by the folder/document retainer  101 . If x≦N, the flow advances to Step S 504 , whereas if x&gt;N, the folder search process illustrated in the flow chart of FIG. 5 is terminated.  
         [0061]    At Step S 504  a score S for the x-th folder f(x) in the folder/document retainer  101  and for the search condition c is calculated by the following equation:  
       S   =         ∑     d   ∈     D        (   x   )                f        (     c   ,   d     )           |     D        (   x   )       |                             
 
         [0062]    The function f is used for judging through pattern matching whether the document contains the search words c. If the document contains the search words c, f(c, d)=1, whereas if it does not contain, f(c, d)=0. This judgement is performed for all documents D(x) of the x-th folder. Therefore, the score S is the number of x-th folder documents containing the search words divided by the total number |D(x)| of documents, and shows a ratio of documents satisfying the search condition to all documents in the x-th folder.  
         [0063]    After the score is calculated at Step S 504 , the flow advances to Step S 505 .  
         [0064]    At Step S 505 , the search result retainer  109  retains the score S calculated at Step s 504  and the corresponding folder number x in an ascending order of values of S. Thereafter, the flow advances to Step S 506 .  
         [0065]    At Step S 506  the value x of the counter is incremented by 1 and thereafter the flow returns to Step S 503 .  
         [0066]    Information (folder label and the like) regarding the candidate folder obtained by the folder search process described with reference to the flow chart of FIG. 5 and retained in the search result retainer  109 , is displayed on the display  206  in correspondence with the search words c, to thereby notify the candidate folder to the user. Folders displayed on the display  206  in the retained order (ascending order of score S) may include all folders retained by the search result retainer  109  or only upper level folders selected in accordance with the score S and the number N.  
         [0067]    During document collection performed by the document processing system of this invention, a folder most suitable for retaining a new document is retained at the top of the candidate folder retainer  104 .  
         [0068]    A user can select the candidate folder easily, by looking at the folder labels near the top thereof retained by the candidate folder retainer  104 . The number of folders having documents matching the search condition designated by the user can be reduced and the document search can be performed efficiently.  
         [0069]    Use of the document processing system of this invention allows a user to retain documents from a user specific viewpoint and to easily collect and search documents.  
         [0070]    In the above example, the function of facilitating both document collection and search is realized. The invention is not limited to this, but a function of facilitating either document collection or document search may also be realized. This example is illustrated in the block diagrams of FIGS. 6 and 7. As apparent from the comparison with the functional structure shown in FIG. 1, the functional structures  601  to  607  shown in FIG. 6 correspond to the functional structures  101  to  107  shown in FIG. 1, and the functional structures  701  to  704  shown in FIG. 7 correspond to the functional structures  101 ,  107 ,  108  and  109  shown in FIG. 1.  
         [0071]    In the example shown in FIG. 1, the candidate folder for each document is searched and displayed to facilitate document collection. The invention is not limited thereto. In another example, a newly arrived document is sorted into a particular folder suitable for the document and the sorting result or folder is displayed to facilitate document collection. This example will be described with reference to the functional structure shown in FIG. 8.  
         [0072]    In FIG. 8, reference numeral  801  represents a folder/document retainer for retaining folders and documents belonging to each folder. Reference numeral  802  represents a new document retainer for retaining a newly arrived document. Reference numeral  803  represents a document sorter for sorting the document retained by the new document retainer  802  into a particular folder suitable for the document. Reference numeral  804  represents a sorting result retainer for retaining the result sorted by the document sorter  803 . Reference numeral  805  represents a document retainer for retaining a document to be saved. Reference numeral  806  represents a folder generator for generating a folder for a document retained by the document retainer in accordance with the sorting result retained by the sorting result retainer  804 . Reference numeral  807  represents a folder retainer for retaining the folder generated by the folder generator  806 . Reference numeral  808  represents a folder changer for changing the folder retained by the folder retainer  807 . Reference numeral  809  represents a saving processor for controlling the folder/document retainer  801  to retain the document retained by the document retainer  805  in the folder retained by the folder retainer  807 .  
         [0073]    In this example, the sorting result retainer  804  stores a list of documents sorted for each folder f. The document retainer  805  retains one document before it is saved. The folder/document retainer  801 , new document retainer  802 , and folder retainer  803  have the same structures as those of the retainers  101 ,  102  and  105  described with FIG. 1.  
         [0074]    The structure for performing each function of the system shown in FIG. 8 is the same as described with FIG. 2, and the description thereof is omitted.  
         [0075]    With reference to the flow chart shown in FIG. 9, the operation of a document sorting process to be executed by each function shown in FIG. 8 will be described.  
         [0076]    At Step S 901  it is checked whether the new document retainer  802  has retained the text t(n) of a newly arrived document. If retained, the flow advances to Step S 902 , whereas if not, Step S 901  is repeated until the new document retainer  802  retains the text t(n) of a new document.  
         [0077]    At Step S 902  a feature vector v(dn) of the text t(n) is generated, this feature vector and the text t(n) being retained by the new document retainer  802 . Thereafter, the flow advances to Step S 903 .  
         [0078]    At Step S 903  the value x of a counter is initialized to 1. The counter is used for counting a folder number and sequentially accessing folder information retained by the folder/document retainer  801 . Thereafter, the flow advances to Step S 904 .  
         [0079]    At Step S 904  the value x of the counter is compared with the number N of folders retained in the folder/document retainer  801 . If x≦N, the flow advances to Step S 905 , whereas if x&gt;N, the process is terminated.  
         [0080]    At Step S 905  a score S=g(v(dn), v(fx)) is calculated where f(x) is the x-th folder retained by the folder/document retainer  801  and d(n) is a new document. After the score is calculated, the flow advances to Step S 906 .  
         [0081]    At Step S 906  the score S calculated at Step S 905  is compared with a preset threshold value Sc. If S&gt;Sc, the flow advances to Step S 907 , whereas if S≦Sc, the flow advances to Step S 908 .  
         [0082]    At Step S 907 , the new document d(n) is added to the set of documents corresponding to the folder f(x) retained in the sorting result retainer  804 .  
         [0083]    At Step S 908  the value x of the counter is incremented by 1 and thereafter the flow returns to Step S 904 .  
         [0084]    In a folder generating process, the folder retainer  807  retains all folders associated with the sorting result retainer  804  to which documents retained by the document retainer  808  belong. In a folder changing process, a user adds a folder to, or deletes a folder from, the folder list retained by the folder retainer  807 . The saving process is the same as that shown in the flow chart of FIG. 4.  
         [0085]    With the above processes, during document collection, the document to be saved is sorted into a particular folder which is in turn retained by the sorting result retainer  804 . Documents in the folder sorted and retained by the sorting result retainer are searched by a user. The user can therefore search the whole body of relevant documents from a user specific viewpoint. The saving process may be performed only upon reception of a save instruction if the folder retainer  807  retains a default folder and a change instruction is not input from the input device  207 . As above, use of the document processing system of this invention allows a user to search documents and obtain a suitable folder from a user specific viewpoint so that document collection becomes easy.  
         [0086]    In the above example, a proper folder is generated in accordance with the sorting result, and a user checks this folder and, if necessary, changes it. The invention is not limited to this, but the folder may be changed while checking the candidate folder determined by the candidate folder forming process shown in FIG. 1 to facilitate document collection. This example will be described with reference to the functional structure shown in FIG. 10.  
         [0087]    In FIG. 10, reference numeral  1001  represents a folder/document retainer for retaining folders and documents belonging to each folder. Reference numeral  1002  represents a new document retainer for retaining a newly arrived document. Reference numeral  1003  represents a document sorter for sorting the document retained by the new document retainer  1002  into a particular folder suitable for the document. Reference numeral  1004  represents a sorting result retainer for retaining the result sorted by the document sorter  1003 . Reference numeral  1005  represents a document retainer for retaining a document to be saved. Reference numeral  1006  represents a folder generator for generating a folder for a document retained by the document retainer in accordance with the sorting result retained by the sorting result retainer  1004 . Reference numeral  1007  represents a folder retainer for retaining the folder generated by the folder generator  1006 . Reference numeral  1008  represents a candidate folder generator for generating as a candidate folder a folder suitable for a document retained by the document retainer  1005 , excepting the folder retained by the folder retainer  1007 . Reference numeral  1009  represents a candidate folder retainer for retaining the candidate folder generated by the candidate folder generator  1008 . Reference numeral  1010  represents a folder changer for changing the folder retained by the folder retainer  1007  and the candidate folder retained by the candidate folder retainer  1009 . Reference numeral  1011  represents a saving processor for controlling the folder/document retainer  1001  to retain the document retained by the document retainer  1005  in the folder retained by the folder retainer  1007 .  
         [0088]    In this example, the folder/document retainer  1001 , new document retainer  1002 , sorting result retainer  1004 , and folder retainer  1007  have the same structures as the structures  901 ,  902 ,  904 , and  907  shown in FIG. 9. The candidate folder retainer  1008  has the same structure as the structure  104  shown in FIG. 1. Each process is also the same as that described earlier. However, the folder changing process is partially different. In the folder changing process of this example, the folder deleted from the folder retainer  1007  is retained by the candidate folder retainer  1009 . If the candidate folder retained by the candidate folder retainer  1009  is added to the folder retainer  1007 , this candidate folder is deleted from the candidate folder retainer  1009 .  
         [0089]    With the above processes, in changing the sorting result and determining a final folder, an additional folder can be easily found so that document collection becomes easier.  
         [0090]    In the examples described above, the score is calculated by using distance relationship between feature vectors in the candidate folder search process and document sorting process. The invention is not limited only to this, but other methods may be used for the calculation of a score which indicates a degree of possibility of a document belonging to the folder. For example, a search condition c composed of a user keyword and its logical relationship may be added to the folder data to use: 
           f =( l, D, c, v ( f )), 
         [0091]    and calculate a score S=f(c(x), d(n)). The score may also be calculated as: 
           S=f ( c ( x ),  d ( n ))× C+g ( v ( fx ),  v ( dn )) 
         [0092]    where C is a constant.  
         [0093]    The invention is not limited only to the folder search process using the search condition c composed of a user keyword and its logical relationship. Other methods of searching a folder may be used. For example, another folder f(t) similar to a folder to be actually searched may be used as the search condition to calculate the score S=g(v(fx), v(ft)). Alternatively, a document d(t) having similar contents to a folder to be actually searched may be used as the search condition to calculate the score S=g(v(fx), v(dt)).  
         [0094]    In the above example, only the folder searcher is used for searching a folder. The invention is not limited thereto, but a document searcher for searching a document may be used.  
         [0095]    In the above example, the document sorter sorts a document into specific one of all folders. The invention is not limited thereto, but a document may be sorted into specific one of limited folders. For example, folders designated by a user may be used, or folders used in a predetermined past time period may be used.  
         [0096]    In the above example, the score is calculated by the same method for all folders and compared with the same threshold value in the document sorting process. The invention is not limited thereto, but the score calculation method may be changed for each folder or the threshold value may be changed for each folder.  
         [0097]    In the above example, the candidate folder search process and folder search process retain all final folders as the search result. The invention is not limited thereto, but only some folders may be retained as the search result. For example, folders whose scores are in excess of a preset threshold value may be retained, or folders whose scores are in a preset range of values or rates may be retained.  
         [0098]    In the above example, when a document is collected, a new folder is not generated. The invention is not limited thereto, but a new folder generator may be provided which generates a new folder and adds it to the folder retainer.  
         [0099]    In the above embodiment, the sorting result is always retained in the sorting result retainer. The invention is not limited thereto, but a sorting result deleting unit may be provided which deletes the sorting result after the document is saved or which deletes the sorting result of only a particular folder.  
         [0100]    In the above example, the value of the function f is calculated for documents stored in a plurality of folders in the folder search process. The invention is not limited thereto, but the value of the function f may be calculated only once for one document. For example, the value of the function f calculated once may be stored, or after the value of the function f is calculated for a document, the calculated value is sent to the folder to which the document belongs and the score received folder by folder is synthesized to derive the folder score.  
         [0101]    In the above example, the value of the function f is calculated through pattern matching. The invention is not limited thereto, but an index for a document may be generated to calculate the value of the function f by using this index.  
         [0102]    A different example of the judgement of coincidence between the search condition and the folder to be executed by the folder searcher  108  of FIG. 1 will be described. The term “document set” used in FIG. 11 and in the description of the specification corresponds to the term “folder” used in FIG. 1 and in the description of the specification.  
         [0103]    In FIG. 11, reference numeral  1101  represents a document retainer for retaining documents to be searched. Reference numeral  1102  represents a document set retainer for retaining a set of documents. Reference numeral  1103  represents a search condition retainer for retaining a search condition. Reference numeral  1104  represents a document searcher for searching a document satisfying the search condition retained by the search condition retainer  1103 . Reference numeral  1105  represents a search result retainer for retaining a search result of the document searcher  1104 . Reference numeral  1106  represents a document set score calculator for calculating a score of each document set retained by the document set retainer  1102  by using the search result retained by the search result retainer  1105 . Reference numeral  1107  represents a document set score retainer for retaining a score calculated by the document set score calculator  1106 .  
         [0104]    In this example, the document set retainer  1102  stores a list of document numbers of a document set added with a set number specific to each document set. An example of the document set retainer is shown in FIG. 13. A column  1301  stores identification set numbers added to respective document sets, and a column  1302  stores lists of document identification numbers.  
         [0105]    The document retainer  1101  stores the text of each document added with a document number specific to the document. The search condition retainer  1103  stores a list of search words. The search result retainer  1105  stores a list of document numbers. The document set score retainer  1107  stores the score of each document set identified by the set number.  
         [0106]    With reference to the flow chart shown in FIG. 12, the operation of the search process will be described.  
         [0107]    At Step S 1201  it is checked whether the search condition retainer  1103  has retained a search condition c constituted of a list of search words. If retained, the flow advances to Step S 1202 , whereas if not, Step S 1201  is repeated.  
         [0108]    At Step S 1202  documents satisfying the search condition c retained by the search condition retainer  1103  are searched from the documents retained by the document retainer  1101 . Whether the text of each document contains each word of the search condition c is checked through pattern matching. If the text contains all search words, it is judged that the document satisfies the search condition c. The document number of the document satisfying the search condition is retained by the search result retainer  1105 . Thereafter, the flow advances to Step S 1203 .  
         [0109]    At Step S 1203  the value k is set to 1. Thereafter, the flow advances to Step S 1204 .  
         [0110]    At Step S 1204  the value k is compared with the number N of document sets retained in the document set retainer  1102 . If k≦N, the flow advances to Step S 1205 , whereas if k&gt;N, the process is terminated.  
         [0111]    At Step S 1205 , a score s k  of the k-th document set D k  in the document retainer  1102  is calculated by using an F distribution with a degree of freedom (φ 1 , φ 2 ) by the following equation:  
         s   k     =       φ   2           φ   1            F     φ   1       φ   2            (   α   )         +     φ   2                               
 
         [0112]    where n is the number of documents in the document set D k , x is the number of documents in the search result retainer  1105  among those documents belonging to D k , φ 1  is 2(n−x+1), and φ 2  is 2x. α is a parameter for designating a reliability in interval estimation, for example, α=0.1. The flow thereafter advances to Step S 1206 .  
         [0113]    At Step S 1206 , the score s k  calculated at Step S 1205  is retained by the document set score retainer  1107 . Thereafter, the flow returns to Step  51204 .  
         [0114]    For example, in the example of the document set retainer shown in FIG. 13, it is assumed that the document number obtained as the search result after Step S 1202  is (1, 3, 5). The values n and x of each of the document sets  1  to  3  are n=5 and x=3 for D 1 , n=1 and x=1 for D 2 , and n=3 and x=1 for D 3 . Therefore, the scores s k  of the document sets are given by:  
         s   1     =       6       6          F   6   5          (   0.1   )         +   6       ≃   0.25               s   2     =       6       2          F   2   2          (   0.1   )         +   2       ≃   0.10               s   3     =       6       6          F   5   2          (   0.1   )         +   2       ≃   0.03                           
 
         [0115]    With the above search method, a high score is given to the document set satisfying the search condition (i.e., a document set containing many documents matching the search condition). Therefore, by using the calculated scores, a user can easily search the document set matching the search condition.  
         [0116]    In the above example, the number of elements of a document set and the number of elements of the document set satisfying the search condition are used to perform statistical interval estimation of binomial distribution, and its lower limit value is used as the score of the whole document set.  
         [0117]    In the following example, the number of elements of a document set and a score for the search condition for each element are used to perform interval estimation of population mean, and its lower limit value is used as the score of the whole document set.  
         [0118]    The fundamental structure of this example is the same as that shown in FIG. 11. However, the document searcher  1104  calculates a score for the search condition of each document, and the search result retainer  1105  retains a score of each document. An example of the search result retainer  1105  is shown in FIG. 15. A column  1501  stores document numbers and a column  1502  stores scores of the documents.  
         [0119]    With reference to the flow chart shown in FIG. 14, the operation of the search process will be described.  
         [0120]    At Step S 1401 , it is checked whether the search condition retainer  1103  has retained a search condition c constituted of a list of search words. If retained, the flow advances to Step S 1402 , whereas if not, Step S 1401  is repeated.  
         [0121]    At Step S 1402 , a score for the search condition c retained by the search condition retainer  1103  and for documents retained in the document retainer  1101  is calculated. This score is calculated by using occurrent frequency of each word of the search condition c in the text of each document. The calculated score is retained by the search result retainer  1105 . Thereafter, the flow advances to Step S 1403 .  
         [0122]    At Step S 1403 , the value k is set to 1. Thereafter, the flow advances to Step S 1404 .  
         [0123]    At Step S 1404 , the value k is compared with the number N of document sets retained in the document set retainer  1102 . If k≦N, the flow advances to Step S 1405 , whereas if k&gt;N, the process is terminated.  
         [0124]    At Step S 1405 , an unbiased estimator V is calculated by the following equation if n&gt;1:  
       V   =       ∑       (     x   -     x   _       )     2         n   -   1                             
 
         [0125]    where n is the number of documents in the k-th document set D k  retained in the document set retainer  1102 , and x is a mean score of documents belonging to D k . The score s k  is calculated by using the degree of freedom φ and the t distribution of double side probability α:  
         s   k     =       x   _     -       t        (     φ   ,   α     )              V       n                                 
 
         [0126]    The degree of freedom φ is n−1. If n=1, then 
         
       s 
       k 
       =α{overscore (x)} 
     
         [0127]    wherein α is a parameter for designating a reliability in interval estimation, for example, α=0.1. The flow thereafter advances to Step S 1406 .  
         [0128]    At Step S 1406 , the score s k  calculated at Step S 1405  is retained by the document set score retainer  1107 . Thereafter, the flow returns to Step S 1404 .  
         [0129]    In the above example, an AND operation is performed among search words of the search condition. The invention is not limited thereto, but optional search conditions for documents may be used such as other logical relationships and search word positions in each document.  
         [0130]    In the above examples, document search is performed through pattern matching. The invention is not limited thereto, but other optional search methods may be used. For example, an index may be set to each document to search a document by using the index.  
         [0131]    In the above examples, information constituting a set is a document. The invention is not limited thereto, but optional information may be used such as a record which is a set of data. In this case, search methods suitable for respective information are used.  
         [0132]    In the above examples, a score is calculated for each set. The invention is not limited thereto, but sets may be retained and the score for the set containing at least one document in the search result may be calculated. The scores of other sets are 0.  
         [0133]    In the above examples, scores for all sets are retained. The invention is not limited thereto, but only some scores may be retained. For example, scores in excess of a preset threshold value may be retained or scores in a predetermined range of values and ratios may be retained.  
         [0134]    In the above examples, each function is realized on the same computer. The invention is not limited thereto, but each function may be realized on computers and processors distributed on a network.  
         [0135]    In the above examples, the search condition retainer, search result retainer, and document set score retainer are realized by a RAM, and the document retainer and document set retainer are realized by a disk. The invention is not limited thereto, but optional storage devices may be used.  
         [0136]    In the above examples, programs are stored in ROM. The invention is not limited thereto, but they may be stored in other storage devices or they may be realized by circuits which provide such program functions.  
         [0137]    Obviously, the invention may be embodied by supplying a storage medium storing software program codes realizing the functions of the invention to a system or apparatus whose computer (CPU or MPU) runs by reading the program codes stored in the storage medium.  
         [0138]    In this case, the software program codes read from the storage medium themselves realize the functions of the invention. Therefore, the storage medium storing the program codes constitutes the invention.  
         [0139]    The storage medium storing such program codes may be a floppy disk, a hard disk, an optical disk, a magnetooptical disk, a CD-ROM, a CD-R, a magnetic tape, a non-volatile memory card, and a ROM.  
         [0140]    Obviously, such program codes are other types of this invention, not only for the case wherein the functions of the invention are realized by executing the program codes supplied to the computer but also for the case wherein the functions are realized by the program codes part or the whole of which is used with an OS (operating system) on which the computer runs.  
         [0141]    Furthermore, the functions of the invention may also be realized by a system wherein in accordance with the program codes stored in a memory of a function expansion board or unit connected to the computer supplied with the program codes, a CPU or the like of the function board or unit executes part or the whole of the actual tasks.  
         [0142]    Obviously, the invention is also applicable to the case wherein the software program codes realizing the functions of the invention stored in a storage medium are supplied to a requestor via communication lines such as personal computer communications.