Abstract:
An electronic-document management system includes an acquisition unit, an edit unit, first and second storage units, a generation unit and an output unit. The acquisition unit acquires a target electronic document. The edit unit edits the acquired target electronic document. The first storage unit stores the target electronic document edited by the edit unit and a feature value of the edited target electronic document in association with each other. The generation unit generates meta-information of the edited target electronic document, which comprises a feature value of the edited target electronic document. The second storage unit stores the meta-information of the edited target electronic document and a feature value of the meta-information of the edited target electronic document in association with each other. The output unit outputs the feature value of the meta-information of the edited target electronic document as reference information of the edited target electronic document.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The invention relates to an electronic-document management system and a method and in particular to an electronic-document management system and a method, which are capable of realizing traceability of an electronic document. 
         [0003]    2. Related Art 
         [0004]    As importance of an electronic document in life in society becomes higher, importance of traceability of the electronic document is recognized. The traceability of the electronic document means that a history of document distribution is recorded and document distribution is later specified from the record. 
       SUMMARY 
       [0005]    According to an aspect of the invention, an electronic-document management system includes an acquisition unit, an edit unit, first and second storage units, a generation unit and an output unit. The acquisition unit acquires a target electronic document. The edit unit edits the acquired target electronic document. The first storage unit stores the target electronic document edited by the edit unit and a feature value of the edited target electronic document in association with each other. The generation unit generates meta-information of the edited target electronic document, which comprises a feature value of the edited target electronic document. The second storage unit stores the meta-information of the edited target electronic document and a feature value of the meta-information of the edited target electronic document in association with each other. The output unit outputs the feature value of the meta-information of the edited target electronic document as reference information of the edited target electronic document. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    Exemplary embodiments of the invention will be described in detail based on the following figures, wherein: 
           [0007]      FIG. 1  is a drawing to show an electronic-document management system according to an exemplary embodiment of the invention; 
           [0008]      FIG. 2  is a drawing to show the configuration of a document management database; 
           [0009]      FIG. 3  is a drawing to show the configuration of a document-unit edit history database; 
           [0010]      FIG. 4  is a drawing to show the configuration of a user-unit edit history database; 
           [0011]      FIG. 5  is a flowchart to show registration processing of a new document in a user client; and 
           [0012]      FIG. 6  is a flowchart to show document edit processing in the user client. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    Referring now to the accompanying drawings, exemplary embodiments of the invention will be described. 
         [0014]      FIG. 1  is a drawing to show the general configuration of an electronic-document management system according to an exemplary embodiment of the invention. As shown in  FIG. 1 , an electronic-document management system  10  includes a plurality of document management databases  18 , a plurality of edit history databases  12 , and a plurality of user clients  16 . These components  12 ,  16 ,  18  of the electronic-document management system  10  are connected to a communication network  14 . The document management database  18  is a database system implemented by a known server computer and has a configuration shown in  FIG. 2 . That is, the document management databases  18  store entities of various electronic documents and meta-information of the electronic documents (described later) in association with hash values (which are an example of feature values) of the electronic documents. Electronic documents include newly created electronic documents and electronic documents provided by editing any electronic document. For one electronic document, entity of the one electronic document and a hash value of the one electronic document are registered in the document management database  18  in association with each other. Also, meta-information of the one electronic document and a hash value of the meta-information of the one electronic document are registered in the document management database  18  in association with each other. A user is notified of the hash value of the meta-information of the one electronic document as reference information of the one electronic document relevant to the meta-information. Each meta-information contains a hash value of an electronic document relevant to the meta-information. When transmitting reference information of an electronic document to the document management database  18 , the user client  16  receives the meta-information of the electronic document as a reply. When again transmitting the hash value contained in the returned meta-information of the electronic document to the document management database  18 , the user client  16  receives the electronic document associated with the transmitted hash value as a reply. 
         [0015]    Like the document management database  18 , the edit history database  12  is a database system implemented by a known server computer. The edit history database  12  includes a document-unit edit history database having configuration shown in  FIG. 3  and a user-unit edit history database having configuration shown in  FIG. 4 . As shown in  FIG. 3 , the document-unit edit history database stores reference information (a hash value of meta-information) of a new document and reference information (a hash value of meta-information) of a document provided by editing the new document once or plural times in association with each other. As shown in  FIG. 4 , the user-unit edit history database stores reference information of documents, which are newly created or edited by each user, in association with a user identifier of the user. 
         [0016]      FIG. 5  is a flowchart to show processing of registering a new electronic document into the electronic-document management system  10 . As shown in  FIG. 5 , if a new electronic document is prepared using a word processing application software or a spreadsheet application software, for example, in the user client  16 , the user client  16  calculates a hash value of the new electronic document (S 101 ). The user client  16  associates the newly created electronic document (entity) and the hash value of the newly created electronic document with each other and transmits to any of the document management databases  18 , to register the new electronic document and the hash value of the new electronic document in the document management database  18  in association with each other (S 102 ). Further, the user client  16  generates meta-information of the new electronic document including (i) the hash value of the new electronic document, which is generated at S 101 , (ii) creation date and time of the newly created electronic document, and a user identifier of a user who is a creator, for example, in an XML document format (S 103 ). The user client  16  also calculates a hash value of the thus-generated meta-information of the new electronic document (S 104 ). 
         [0017]    The user client  16  also transmits the thus-generated meta-information of the new electronic document and the hash value of the meta-information of the new electronic document to any of the document management databases  18 , to register the meta-information of the new electronic document and the hash value of the meta-information of the new electronic document in the document management database  18  in association with each other (S 105 ). Further, the user client  16  transmits the user identifier of the user who newly creates the document and the hash value of the meta-information of the new electronic document calculated at S 104  (reference information of the newly created document) to the edit history database  12 , to register those information (the transmitted user identifier and the transmitted hash value) in the document unit history database and the user-unit edit history database (S 106 ). That is, a new record is created in the document-unit edit history database and the hash value of the meta-information of the new electronic document calculated at S 104  is registered into a column “reference information of new document.” Also, the hash value of the meta-information of the new electronic document calculated at S 104  is registered in the user-unit edit history database in association with the user identifier. 
         [0018]    Then, the user client  16  displays the hash value of the meta-information of the new electronic document calculated at S 104 , for example, on a display as reference information of the newly created document (S 107 ). Alternatively, the user client  16  may create a file having the hash value of the meta-information of the new electronic document as a value. The reference information thus output is sent to another user by means of, for example, an electronic mail. Also, as described above, by transmitting reference information to the document management database  18 , the user client  16  can acquire an electronic document corresponding to the transmitted reference information. 
         [0019]    Each document management database  18  registers electronic documents and meta-information of the electronic documents in association with hash values of the electronic documents and hash values of the meta-information of the electronic documents, respectively. For example, a cryptographic hash function having collision tolerance, such as SHA-256, may be used. Thereby, collision between hash values can be virtually ignored and each document management database  18  can be used as a distributed database. 
         [0020]      FIG. 6  is a flowchart to show processing of editing an electronic document in the electronic-document management system  10 . In the case where a user who acquires reference information of a newly created electronic document or an electronic document edited by another user as described above is to edit the acquired electronic document using the user client  16 , the user client  16  acquires the reference information of the electronic document to be edited (which may be referred to as a “target electronic data”), acquired by the user (S 201 ). The user client  16  reads the target electronic document from any of the document management databases  18  based on the reference information of the target electronic document (S 202 ). Then, the electronic document acquired at S 202  is edited using a word processing application software and/or a spreadsheet application software, for example (S 203 ). 
         [0021]    The user client  16  calculates a hash value of the edited target electronic document (S 204 ) and transmits the edited target electronic document and the hash value of the edited target electronic document to any of the document management databases  18 . Thus, the edited target electronic document and the hash value of the edited target electronic document are registered in the document management database  18  in association with each other (S 205 ). 
         [0022]    Subsequently, the user client  16  generates meta-information of the edited target electronic document, which includes (i) the hash value of the edited target electronic document, (ii) the reference information of the target electronic document (edit source) acquired at S 201 , (iii) edit date and time, and (iv) a user identifier of the user who is an editor, for example, in an XML format (S 206 ). The user client  16  generates the hash value of the generated meta-information of the edited target electronic document and transmits the meta-information of the edited target electronic document and the hash value of the meta-information of the edited target electronic document to any of the document management databases  18 , to register the transmitted meta-information and the transmitted hash value in the document management database  18  in association with each other (S 207 ). 
         [0023]    Further, the user client  16  transmits to the edit history database  12  the user identifier of the user who edits the target electronic document, the hash value of the meta-information of the edited target electronic document calculated at S 207  (reference information of the edited target electronic document) and the reference information of the target electronic document (edit source) acquired at S 201 , to register transmitted information (the transmitted user identifier, the transmitter has value, the transmitted reference information) in the document-unit history database and the user-unit edit history database (S 208 ). That is, the document-unit edit history database is searched for a record where the reference information of the target electronic document acquired at  201  is recorded as reference information of a new document or reference information of an edited document and then, the hash value of the meta-information of the edited target electronic document calculated at S 207  is registered in column “reference information of edited document” of the record. The hash value of the meta-information of the edited target electronic document calculated at S 207  is registered in the user-unit edit history database in association with the user identifier. 
         [0024]    Then, the user client  16  displays the hash value of the meta-information of the edited target electronic document calculated at S 207 , for example, on the display as the reference information of the target electronic document edited by the user (S 209 ). Alternatively, the user client  16  may update the file having the hash value as a value. The thus-output reference information of the edited target electronic document is sent to another user by means of, for example the electronic mail. When this reference information of the edited target electronic document is transmitted to the document management database  18 , the corresponding edited target electronic document can be obtained, as described above. 
         [0025]    The foregoing description of the exemplary embodiments of the invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The exemplary embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.